When I learned today that Helium offers 5% of the earnings of friends you invite to join I was a bit surprised and I felt like making a little overview of what different communities offer.
Here's what you get:
Ciao
-50p as a one-time payment
-50% of your friend's earnings, but only for 6 months
Dooyoo
-no referral program as far as I know
Trivago
-30% ongoing (+additional 10% for "mentoring" of your friend, if eligible)
Helium
-5% ongoing
Feel free to share your views. You know, I'm totally biased, but I must say I find the incentive that trivago offers the only one that deserves the name...