Of course it can be interesting (depending on how much you want to earn). Even if most of them will bring you almost nothing (or nothing at all), some are profitable (and especially it's free).

The best is to choose them well (or to make them all), there will surely be some who will go far (personally I prefer to choose 2 or 3 interesting)
On the other hand it's improbable you'll get rich with it, but it can create seed money (to become rich after  )