Next.
I'm working my existing software engineer job while I build up my customer base on my side businesses. Your interviews and shit riddles can fuck right off.
The best part is when the riddle (perhaps their explanation) doesn't make sense, or the coding test doesn't work because there is a firewall on the guest wifi that prevents it, etc.
I had a startup interview last year where they were a well-funded start up full of PhDs. Had a hiring screen (with non-trivial code), a full day of interviews over the phone/etherpad, a conversation + coding interview with the frickin CTO. This was to decide weather to fly me to the Bay are for the actual interview (was on the East coast). I had a full-time, high workload job at the time (constant crunchtime) ... so this was brutal on me. Never doing this again.
I am with you though in principle. Some fizzbuzz-like test is OK, I understand they want to know if you can code at all. Something like code review where you think aloud is fine too. But take home assignments, whiteboard coding, huh.. An acquaintance of mine had to conjure a working spreadsheet application in one and a Space Invaders clone in the other. Mind you, none of the jobs had anything to do with spreadsheets or gaming.
If my living would depend on it I'd do it, no question. But in a relatively liquid job market of today I'd ether pass or offer to do it at a competitive hourly rate.