The more people I talk to, the more I realize that bats in houses is a bit of a common occurrence! I just wanted to mention that there ARE ways to exclude bats that will not harm them.
There are a couple of great websites with information on the proper way to exclude bats. The one I trust the most is http://www.batcon.org/ This is the website for Bat Conservation International.
It also has lots of great information about bats and why they are so incredibly important to our ecosystem (did I ever mention that one little brown bat can eat up to 1000 mosquito sized insects in an hour?). A recent study also estimated that if we were to lose all bats from the United States it would cost us 3.7 billion dollars a year to take care of the insect issue they would leave behind.
I know that many people are worried about bats in and around their house, mostly because of the concern of rabies. Truth be told, the chances of a bat having rabies is pretty slim. From the Bats of Ohio Book by Virgil Brack et al. "Worldwide, rabies kills about 30,000 people each year, 99 percent of those cases are transmitted by dogs. During the last 50 years, only about 40 people in the United States died from rabies after being bitten bat a bat".
Bats, like any other mammal, can, of course, contract rabies....so can deer, raccoons, skunks, foxes, and domestic animals (among others). The best precaution is that no wild animal should be touched with your bare hand and if you are bitten rabies shots it is (regardless of the animal that bit you).
Another myth..bats cannot and will not get tangled in your hair. They want to avoid you as much you want to avoid them. If you are outside at night and there is a bat around, its because they have come after the yummy insects you have attracted!