Originally Posted by Samvel Hovhannisyan
1. is it legally ok to ask/buy points from others?
Welcome to Flyertalk.
The USA version of Membership Rewards only permits transfers to the frequent flyer accounts of cardholders. To fully comply with this rule each and every one of your friends would need to make you an Authorized User on their American Express card account. In practice this rule is seldom enforced, but you should be aware of it.
I do not know how Aeroplan would react if you start to receive transfers from a dozen different American Express accounts. It would probably be better to use several different Aeroplan accounts, each in the name of one of the travelers, and have each receive points only from a few different American Express accounts.