From my perspective it doesn't seem like much of a risk--no more than any other job, and probably less than most.

Even if Twitter flames out and gets sold, it's a highly recognizable name, and will be from a long time. It's a name that jumps off the page of a resume. It will help you get through HR filters for a long time to come.

And particularly in the anti-abuse space, going to work at Twitter has to be like going to play in the major leagues.