There is potential for abuse.. especially in the pinkie forums. I've caught multiple suspicious promoters blatantly lying about "news" to pump a pink corpse. For a couple bucks, these types of people can ensure that their own piles of BS stay promoted right at the top of the thread.. they can just continue to award their own posts Plus1.
If IHub doesn't want to remove the "self-promotion" functionality completely, one modification that could help prevent abuse is to provide some small notification flag, symbol or button on the post IF it was Plus1-ed by the author him/herself. I.e. just a note that informs the community it's self-promotion, and not based on community opinions.
Then down the road, if you want to take it further, you could add a counter.. Perhaps a small flag should be present when, for example, 50% or more of the awarded Plus1 came from the original author?