Those seem to be our most frequent haunts. A vampire is a person who for whatever reason lacks energy - can't keep it worth a darn. This site has a bit of a bias toward blood-feeding, because I happen to feed on blood and because there needs to be a site which hypes sanguinary safety. It's quite possible to feed without feeding on blood, but in my opinion, blood is the most efficient way of getting the life energy that we need. The blood is the life.
Blood carries a great deal of life force.
Bloodletting releases that force, as well as a lot of other energy depending on the circumstances. There are several definitions of vampires in the dictionary, including one from the early twentieth century, which refers to a sexually adventurous woman as a vampire. Vampirism is used metaphorically these days to describe any sort of leeching, whether it refer to blood, money, ego strokes, or whatever. Either by drawing blood, or by psychically draining life force from a subject. It's much better to use a willing donor, as this doesn't raise issues of rape and theft.