Since the dotcom crash and burn of 2000 the sites are pretty useless for racking up free points. After 40,000 Mypoints in 13 months I have struggled to get the last 1000 points and it has taken nearly 10 weeks. Pretty useless for air mileage accumulation.
Clickrewards has been pretty hard to get miles lately. The good shopping bonuses are few and far between.
All in all it is still possible to pull in a few thousand free air miles a month through clicking and most of those tips are here on FT. Last year it was pretty easy to rack up 5000 ff miles a week. I think we will look back on 2000 in years to come as the year of the "free lunch" (at least on the airplane flights).