I read this the other day. Interesting stuff, and it made me respect a few companies a little less. For example, Guild Wars 2 may be great, but it's got some of these tricks in it (tertiary currency you can buy with real money, pain removal in at least the form of bag/bank space).
Interesting bit about the human brain being more vulnerable before age 25. That I didn't know. Thanks for the link. I'll probably refer to it in other conversations in the future.
This explains my friends. The group I play MMOs with sometimes flocks to a F2P game. I never spend money, they always do. I'm 34, and they're all 22-23. The most recent example is Neverwinter. We played it for less than a month, a couple guys spent money to get more bag space, and one guy bought a $30 horse. Or maybe they're not so much being tricked as they're just not stingy with their money. I always try to play them without spending a cent, just to see if it's possible.