I think it should be a given that each account will upvote it's own posts. Once. However, I consider the situation of multiple accounts, and how that can drain the Steemit account to extract personal wealth.

The classic problem of the commons.

I haven't thought of a reasonable way to limit the number of accounts an individual can have, or a different valid reason to do so - but this is a valid reason. In the event that Steemit becomes a platform for governance, it will be necessary to limit a person to voting but once.

Anybody else care to share thoughts on this issue?