Now, I have not backed as many Kickstarters as some folks and I have yet to actually feel like I was burned by any of the projects. If you're not in-the-know about Kickstarter, it has gotten a bit of a reputation for people being unhappy about how late their backer rewards end up being. Meaning that individual project managers probably have some fairly optimistic expectations about how fulfillment works, likely because they have never done something like publishing/producing anything on a business-level before. While many of the projects I have backed are still well within their fulfillment windows, I can honestly say that I have only ever gotten one backer reward on time, and that was for a deck of cards I thought looked pretty cool. Everything else has been late relative to the estimated delivery date.
And usually for a good reason or another. Let's get into some examples.
While I did not back it, I understand that the reason why Onyx Path Publishing's premium deluxe hardcore gamer version of Mummy: The Curse was four months late because the printer screwed up the book not once, but twice. This is something entirely out of Onyx Path Publishing's control (aside from saying "What the hell did you do to our books?!" or the like). Yet there are some backers who were screaming bloody murder about it. Now let's be reasonable. Onyx Path is run by Rich Thomas, who has worked with White Wolf Publishing in one capacity or another since the early 90's. It's probably not the first time he's seen a printer screw the pooch and it is likely it won't be the last- in fact I bet it happens a lot more often than the printers or publishers want to admit. Viral Games ran into the same issue, causing a delay for their Engine Heart book.
In fact this brings up another point. Onyx Path and Viral Games both had the book layouts done and ready to go before their Kickstarters went live (I think Viral Games added a few things in as a result of the Kickstarter, but the basic book was done as I understand it). In Onyx Path's case, the Kickstarter was to fund the deluxe premium print run and to put a little money towards more projects for the game line down the road; it's actually their business model. With Viral Games, the Kickstarter was to finance a print run of Engine Heart so that it could be sold in real game stores. In both situations, the delay in fulfillment was caused by screw ups in manufacturing.
Then there are unanticipated problems with the product itself that cause headaches and massive delays. The GCW Zero had an issue with sticky directional pads that the project manager felt compelled to have fixed at great cost, which has had a knock-on effect on getting everything else done. This is a problem that somebody could have easily have just shrugged their shoulders at and shipped the wonky units. But that would have been a real awful thing to do to people, and so he chose to do the responsible thing and make sure the GCW was up to snuff. This, for me at least, falls under 'Acceptable Delay' category since it makes the thing better.
You can also be a victim of your own success, as Steve Jackson Games found out. OGRE Designer's Edition shattered Kickstarter's board game category record for the time, bringing in almost $925k and approximately 5,500 backers. The Kickstarter campaign added a lot of stuff to the game through stretch goals and backer rewards. How much stuff? Well, I seem to recall Steve Jackson saying the box was going to be 14-16lbs, and that was at the start of the Kickstarter. It seems, a year and a half after the campaign has concluded, to have grown to be about the size and weight of a grown man's torso. The box has to not only accommodate the heavy chipboard punch sheets when being shipped, but the assembled 3D counters afterwards and the sheet weight of it all. This necessitated a lot of tests and redesigns of the box so that it could meet all three of those goals. Add on top of that the need to hire a line manager and proof all those sheets, and you have a case of "Sorry guys, we bit off more than we could chew." and "Be patient with us as we get through this." This can be a big problem for smaller or less well-known companies, but Steve Jackson Games has been around for quite awhile and is unlikely to disappear overnight.
For electronic devices, being a victim of your own success can mean that suddenly you cannot source enough parts to build all those extra units people asked for as backer rewards. Electronic components are rarely custom-built these days (unless your name is Hewlett-Packard or Apple); they tend to come in premade units. More than a few electronic gizmo Kickstarters have run face-first into troubles finding enough of a particular component for their product. It isn't like you can simply substitute one part for another; electronics have very specific power requirements that don't play well with substitution. It seems that people have learned from this though, as a lot of hardware type Kickstarter projects will stagger the anticipated delivery of backer reward units to avoid this very issue.
And then there also seems to be the consumer perception that Kickstarter is a pre-order service and that all dates are final and must be observed. It is absolutely nothing like that. It is essentially a means to fund a project with a whole lot of little investments instead of a few big ones. Real investors can tell you that there is always the chance a project will fail and that is why they do as much research into a potential investment opportunity before investing tens of thousands or even hundreds of thousands of dollars into it. Even the best managed projects have delays, it is always a question of what is an acceptable delay and at what point do the investors expect to have no return on their money. This is not really the case with crowdfunding, as the individual amount invested by a given project backer is too miniscule to warrant legal action, meaning there is no workable way for backers to recoup their loss if everything goes south.
The real red flag that you won't get anything is a lack of communication. This is true of real-world projects. If a project manager is avoiding the bigwigs, there's a reason for it and it's usually out of a desire to not get turned into an eggplant (or fired/reprimanded/demoted, if your boss is not a wizard). Similarly, if a Kickstarter project starter has shut down all communication or starts being vague/evasive, start worrying. But otherwise, one must accept that projects (Kickstarter and otherwise) are rarely ever on time and that one must be patient when dealing with it.