I'm a member of both Send Earnings and Inbox $. I've cashed out of both. It takes awhile to get the check, and, they immediately deduct $3 when you cash out for some bogus fee. If you don't mind waiting forever to get to the cashout limit, it's OK to do the clickthrus. Be a little careful on the "offers", tho. I did one of the "free" offers (S&H only, supposedly), and got stuck on a monthly fee deal that I didn't catch on my credit card for several months. Took awhile to get them to credit it back.
Read the "fine print" on the offers!
Also, their "surveys" have gotten REALLY pathetic. First, they use OTX. Second, they pay SQUAT. I just got a survey invite from one of them the other day for, get this, a 45 minute survey for 50 cents!?!?!?! Are they NUTS?!?!?!?