Someone asked why I don't blog more about what I do want, as compared to writing about what I don't want.
The answer is actually straightforward. Just as writers should write about what they know, so should agents represent the types of books they know. I'm what is called a generalist. My reading interests are broad and eclectic, and I therefore feel comfortable representing varied genres in both fiction and nonfiction. Sure, I have my preferences, but I really do feel comfortable handling almost anything (with the exceptions being very traditional romance, erotica, poetry, short stories, novellas, and picture books).
That being said, there are some subjects that just don't appeal to me on a personal level, whether it's because I'm burned out on the subject, or because I feel that it hits too close to home to represent. But whatever the reason, since I truly believe that I need to be as passionate about the work as the author, I've turned down projects that were extremely well-written with a strong publishing viability if I didn't love them. Agents that do sign up authors and projects without feeling that emotional connection typically are the same ones that will bail on you if it doesn't sell after the first five submissions.
So what I can do is from time to time fill you in on things that I know I won't be able to represent passionately. For now, this includes books about the election, religion, the Middle East, business leadership books, and the Peace Corps.
BTW, I've got nothing against the Peace Corps. I've just gotten way too many submissions involving this in the past few months.