Won't the people who want their captchas solved be a bit pissed if a lot of people just load the captcha but decide not to enter anything? I guess the difference to dedicated captcha solving ventures and faucets is that people come there with different expectations.
I guess only a smaller part of people approaching this site would actually start solving captchas right away. You would need at least a page before where you ask for a payout address to continue before getting a captcha from someone else that needs to be solved. Also it might be hard to determine if the captcha really was solved correctly and you should pay out BTC, depending on the API of the captcha-solving "business" you use.
You may have a point, this is more like an mturk thing. Im guessing you could setup a traditional captcha solving thing but people would have accounts and the payout is in btc rather than paypal. With such small amounts paypal taking %3 is a huge cut.