Note, just invite player doesn't mean you get a point
Player has to be active and play in order you to get some point. Also noticed that this doesn't give you quick points so I think buying a nuggets is involved too.
Some interesting facts.
10 FP - well filled pipe
50 FP - 1000 exp
100 FP - 5000$
500 FP - steel lined box
1000 FP - elephant (150% speed)
5000 FP - weapon (just saw melee weapon, but maybe there is ranged option too, will add it soon to twdb)
Haven't seen any report above 5k FP.
So you can see you need much more FP(friend points) to get next reward. I think to prevent abuse its good idea not to make it too easy and also this should bring more players to worlds, well done Inno