Maybe a gittip feature (I don't know if it already does this) is an option to make all donations anonymous so that the recipient does not know the source. This should remove the conflict of interest then.
The flip side of this is someone with an influential blog (high PageRank) etc. can easily use this to smear someone and there's absolutely nothing the target can do about it.
For example, look at Thomas Hawk (aka Andrew Peterson).
In the past, his (occasionally mis-guided) vitriol has been aimed at various targets. It's tapered down since he was sued but it remains appalling how someone with so much pent up anger is able to adversely affect others.
"Shortly afterward Peterson / Hawk caved in, reached an out of court agreement with the museum, removed the allegations of fraud from his blog, and replaced the offending Flickr set with an abject apology so humiliating it’s practically a Private Eye parody."