I actually cleaned up my wishlist over the weekend. I realised that I get spammed by isthereanydeal.com for games that I don't actually want to know about. I managed to bring it down to 77. It needs some more work, but comes in very handy during big sales to see how many games that I would actually buy are discounted.
Even then, a game is 80% off and I think "would I really play this?" and then dont buy it. So now when it comes on sale, and I dont buy it, I remove it from my wishlist.
At the same time, what if Steam feels generous and gives away your wishlist for you!? Then I need more games on the list! (I just had a mini panic attack!)