I don't really like the idea of disincentivizing casting multiple upvotes (or even all of your upvotes) for a single author, because I think there is a fairly common positive scenario where this happens. When I read posts where I can tell that the author really knows what they are talking about, or s/he has a vein of expertise in something I find useful, I will start reading through that author's old posts. It's a handy way of discovering a vein of brilliance in the mountain of nodes out there, and it can often uncover some gems that aren't identified well by the node reputation mechanism.

You could construct an advanced Perl course for yourself simply by reading and understanding all of ikegami's posts, for example. Or I remember when tilly had to bow out of the Monastery, I went through quite a few of his nodes.

When undertaking such an author-centric mining expedition, it's natural to upvote the nodes you really like along the way. In fact, it will probably bring those nodes' reputations more in line with their "true value".

That said, I think that use case is still less common than the more typical "I want to reward this author so I'll randomly pick from his/her nodes and upvote them", which doesn't make the nodes' reputations any more accurate.

Note that planetscape was defending (well, preserving) the practice of topic-centric browsing, partly by saying that it correlates with the presumably undesirable author-centric voting; I am saying that there are not uncommon cases where author-centric browsing is desirable as well.