More annoyingly, it's tough because you're expected to answer whiteboard algorithm questions that closely mimic CS course exam questions but have very little to do with real world programming.

So that stuff you've been doing all day every day for the past 15 years is useless, you have to study for these interviews on your own time. Companies will even send you little study guides with references and strategies for practicing.

Essentially and as far as Google/Facebook/etc are concerned, your experience is worthless and any fresh grad can plug into your role like a cog. Or at least that's what's implied by their selection criteria.