I went to a great seminar a few years ago, it was about people being givers and receivers; most people will give in expectation of receiving. Just as important, most people who receive understand that they should reciprocate in some way.
This works perfectly, until that 'taker' arrives on the scene, you know that person at your work, who is happy to let everyone get them coffee all day, is happy to let everyone else do the grunt work, while they do the high profile stuff.
This isnt imagination, those people really exist, and their typical effect on the give/receive dynamic in a social group; catastrophic.
People start not wanting to risk doing nice things for one another, because now they got the reality thrust in their face, that there may be no return.

The statistics we saw showed that the selfish 'taker' people, transition through social groups quickly, and while they may have some short lived success in the form of promotions at work or becoming a leader in a social group, their inability to be un-selfish ultimately leaves them isolated, and they need to move on.
The seminar had actual statistics that the best way to deal with the 'takers', is to be a chump and keep giving to them, they ultimately undo themselves anyway, and when they have to excuse themselves, you still have the social standing of being a good citizen in the group.

Enjoyed your post, upvoted, resteemed and followed you.