I'm a member of several survey panels, and I spend a few hours each week responding to surveys. Although I get a lot of survey invitations (enough to make my in-box pretty cluttered if I'm away from home for several days), I only actually complete a fraction of those surveys. More often than not, I'll be disqualified because I don't fit the demographic, or because I don't buy the type of products they're surveying about, or because I'm a member of the media and they don't trust me to keep my mouth shut. :-) So the points don't add up as fast as you might expect them to, but they do add up eventually. I agree with those who say that this should not be looked on as a serious income source; rather, it's a hobby that also offers the chance to make a few bucks. Consulting my tax records, I find that since 2008 (when I started doing these regularly) I've made about $400 in rewards. Not a lot, but an extra $10 a month or so to play with. I often spend my reward points on things like gift cards for Starbucks or Amazon.com, since fancy coffees and new books are two treats I love but usually can't justify spending money on. This way, they're freebies. But of course I could use them for more practical things, like clothes, home supplies, or pet supplies.
My current list of survey panels includes: Harris Poll, Opinion Outpost, NFO MySurvey, GlobalTestMarket, and MyPoints (this one is not primarily for surveys; it's mostly a way to get points back when you buy things online, kind of like getting cash back with a credit card. You can also get a few points a day for viewing advertisements.) These are all legitimate survey sites, and I have not been flooded with spam from them, other than the survey invitations themselves. I have not tried Pinecone, but based on the other comments in this thread I will definitely check it out.