Don't get me wrong I appreciate seeing upvotes, but it's not ideal from the point of view of the upvoting angel.
Normally you can just upvote good memes, and scroll past ones you don't like as much, but if you're upvoting everything halfway decent just to counteract the downvote fairy, then your upvote doesn't feel like it really counts for anything.
So eventually you feel like you have to start downvoting memes you don't like, instead of just scrolling past them, as you normally would have.