Hand picking clients to do spec work that can result in tens or hundreds of thousands of dollars isn't a bad idea (aka lawyers). Someone who can take on spec work with the possibility of making two years salary vs someone taking on spec work to make a few weeks worth of salary is completely different. Taking on spec work makes sense if you need the money (I've been there) or you are vying for a very large contract (ad agencies, lawyers etc)...or I guess, if you are positive you can win the work/contract.
I never said spec work doesn't work. I'm simply suggesting that with more care, attention and commitment (especially to spend $) from folks hiring it isn't needed as much ask people think it is.
...and let's be honest here. Folks coming to your site looking for spec work do not fall into the "committed to spend $ on finding the correct person" category. I'm not suggesting that's a bad thing. As one of my replies above state, I think there is room for 99designs, on both sides of the table.
Thanks for taking the time to reply, btw.