There's an official rule, visible when a Merit sources Merits a post:
It is not allowed for merit sources to sell their merit.
I will check that out next time I merit someone, I don't remember seeing it to be honest. That still matches with what theymos said when he touched upon the subject of people getting tagged for the way merits are sent and/or received. Unless they are sold, you shouldn't be tagged according to theymos. Although I am the one who asked the question of meriting yourself, my personal opinion is that it's an abuse of merits, even though the ultimate goal is not to abuse bounties, campaigns, ranking up, etc.