that is true, but not as "true" as people think. not absolutely true.
remember, it is easier to drive traffic to a 4free program counting raw traffic, when you can tell people that they don't need a credit card, won't need a credit card, and will never be asked for one either...
personally i find that a lot of the 4free programs count traffic much better than persign sponsors that are counting 40 to 55% of traffic sent. easy to track through your own clickcount script.
not saying that 4free is supreme at all, but this "600 per day" thing is STILL pissing me off.