i've done the ones for points - at mypoints.com - and tried to do the ones for money.. idon't recall what site it was but before you saw any money (and it was a small amount) you had to accumulate a ridiculous amount of points to get it.
Mypoints, I used to get 10 dollar starbucks gift certificates pretty easily just by visiting pages, or if i was purchasing something, i'd go thru the my points page to get credit for it.. I used to get one every 2 -3 months.