I (as a senior) had a rather bad experience interviewing with Facebook; I was mostly interested in interviewing for whatsapp, the recruiter went and put me in front of someone not at whatsapp, I programmed in an erlang-vm language, so the interviewer was already confused by the code I was writing.

The interview was conducted over coderpad, and at the outset, the interviewer asked if I was familiar with it (I was; I've conducted interviews over coderpad), and I wasted a lot of time commenting out the interviewer's cut and paste instructions and writing out the tests, because when I wanted to actually test out my code, to my surprise, execution was disabled!! I didn't even know that was an option in coderpad.

So, basically one of the key tools I use in my day-to-day coding workflow was kneecapped. As a result I wasn't able to run the quick tests I had written, and I had mixed up two similar algorithms in the implementation, but not in the tests. I would have noticed this IMMEDIATELY if I could have run my code! Needless to say I failed the interview at the first stage.

Oh well. I probably prefer working at startups anyways (I landed at one in the domain I wanted to be in, working in the language I prefer, get paid reasonably well, and have sizable equity in a company that has a good shot at high upside in a short timeframe).