What's caused you to drop a neighbor?

I haven't had to delete anyone yet. I'm still not quite sure how everyone else plays, but I play for me; like I don't spend money on donuts, or get mad when people don't visit my town, even though I visit theirs every day. My town is neat, streets are open, not everything just bunched in a heap...?
I'm actually bummed I made it to lvl 101, all because I took some advice on building houses then selling them after I got the xp. I just need to make more money, not make more levels! But that was my fault. But yeah, back to subject - I haven't deleted anyone yet, but this one town takes ages to load. So much stuff and not enough space! Lol