I think it's important to know know that no one can use you if you cannot be used, refuse to be used.
If you a certain level of popularity, it's because you gained it, or you've lost it. Difference betwen weak, strong. We all start strangers, and no one really had the upper hand before you got to know people, made friends.
Intellectual ability has nothing really to do with it. They really should be begging for your work, not relying on the constant supply of easy plagiarized material. Make them pay for it; in cash, in favours if they're not your "true friends". Deserved anyway.
I think true friends do exist; they're just hard to find amongst everyone else. I have one, or two...three but then
again you can't place complete faith in that.