It doesn't ruin my day, but logging on, and finding 4 Incest stories in a row* in the Recent Unread Topics search with nothing else. Day after day, it's become a bit of a regular disappointment.
(*Though it, varies, of course. Today it was 4 in a row, while other days it might be 6 UA stories, or 10 mixed between those 2.)
I know I talk about this a lot, but it's not like it happens often. It's every single day. I bent over backwards, and pulled out every trick I know, for 6 weeks to get 3 stories. 3 pretty great stories I didn't have to write, but still. It's really annoying when it's so rigidly predictable, and yet never ceases to disappoint me.
We get "New" members, with "New" comments, and "New" requests, but it's all, inevitably, the same thing.