Silverfish like to hang out under Eaves and Shingles, which brings them in contact with your Home and your family.
Silverfish come in a bunch of varieties, are pretty creepy-looking, and get their name from their silvery or gray color. You might recognize their carrot-shaped bodies and tons of antennae sticking out. They move quickly, and like to come out at night. So basically, everything you really want in a bug.
Maybe they're not dangerous, but who wants such creepy, crawly things in their house?