I've personally friended around 20. The in game destiny community is great!
English
#Destiny
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I find people on LFG and delete their friend status (I guess that's what you call it) once I've done what I wanted to do. The only people I've friended for other reasons are a newbie who invited me to do the first mission with him (he has since quit, apparently), someone who I attempted to help through the Vault of Glass, and a guy who hosts a Gorgon Chest giveaway.