If you don't follow back, I unfollow.
The title is pretty self-explanatory, but these people will follow you to then unfollow you if you didn't follow them back. Why can't you be a good person and follow someone because you genuinely like their profile, not because you want them to follow back?

The person who takes forever to reply
Let's say that you PM someone and go a couple days without hearing from them. That's fine. But then they finally reply to you... months later.

This actually happened to me recently. I would really appreciate if people just looked at their messages rather than ignoring them for however long it may be.