@alice44: You can name site, you just can't use referral links.
@OldBuddy: I guess that depends on how you define "problem"... I think when sgluckadoo said slow earnings but no problems, they meant that it may take a long time to reach the cash-out threshold, but as for them paying once you've reached it, they are good about paying. It is not a scam; it just takes a long time to cashout. I used to be active in Inbox Dollars and cashed out twice, but then they changed it from a PTR (Paid-to-read, meaning you get paid to read e-mail ads that they sent you) into a GPT site and now it is much more difficult to reach their threshold.
I also think FC is one of the best. But I am also a part of a few others as well... My way of thinking is that even with FC, you don't make a lot of money with these programs, but if you combine several together, you may add those small streams of income into a true "river" of earnings. I know some people will even join other PTC sites (like ClixSense, for example) and use their earnings from that site to purchase ads to get people to join FC.
You can usually find many different PTC sites, but not all of them remain profitable in the long-term and eventually fold. Thus if you do join one of those sites, make sure that you really check into their backgrounds before investing any money (for upgrades, "rented referrals", etc.) and only spend the money that you can afford to lose. That's one nice thing about cashing out of FC via Paypal... I can keep my on-line earning separate from my "real world" earnings, and thus spend only my on-line earnings for on-line activities and never be afraid of spending more than I can afford to lose. Just this year I lost some money from a site that I thought had long-term potential which ended up folding within a year.
HYIPs are also another option, but those you really have to be careful. Most are simply some type of a Ponzi scheme where you can make money for a few weeks but they eventually fold very quickly and you'll lose any money you have "invested".
One good piece of advice for any of these sites is to try cashing out as soon as you can, esp. for any sites that haven't been around for a long time. You want to actually get a hold of the money you've earned before it folds on you.