Well, in general, and I know this is circular, but ... a lack of people who think like me. Basically, you'll just be there, doing your thing in your natural way, and it will clash with someone important sooner or later. This will hold you back. This can be really stupid stuff like communication styles (or the fact that you talk your way through things while your coworkers don't).

At that point you can jump to another venue and hope for improvement, or try to alter your behavior to be less than genuine. Basically, start acting like someone else at work. The acting thing wears thin sooner or later.

I can dig up a citation for that last claim if you like. I've also written a bunch of my own posts about these topics over the past year or so. http://rachelbythebay.com/w/2011/06/04/fireandforget/ is one of them.