I've been a tutor using this site for quite a long time. They have referred some great clients to me. They work. The problem is they take 35% commission on every session! As a tutor, getting paid $40/hr on average, I simply can't afford that. I tell all of my clients to pay me directly after a while.
Now Wyzant seems to have instituted a system where if you don't bill students for more than 2 sessions they will flag and de-activate your account. Also it is very clear that their admins spy on their tutor's activity, since you will get emails and reminders very soon after you mail students on their website.
You don't have to be psychic to see that they are getting even greedier and now want to eliminate any tutors that aren't giving them total commissions...
Watch out Wyzant, sites like BetterFly.com and ThumbTack.com are poised to take over when you eventually alienate most of your tutor client base.