Owenwil, I am curious to know why you consider these are spammy tactics. Do you consider the tactics used by Dropbox where users were given free space for sharing with friends as spammy? do you also consider sharing something which is valuable to your friend as spammy?

I think it is only spammy if the app misleads the users and sends out messages on their behalf without them knowing. If everything is done in a very transparent manner then I don't think it is spammy at all.