Just so not everyone thinks I'm little miss complain-a-lot and god forbid, a "diva," I want to share with you a few reasons that may benefit you if you do bother to do signings. I've been working at a large bookstore for years so this is from experience. There are certain bookstores that have rules--if you sign a stock of books then the store cannot return them. The usual deal is that unless your book sells like hotcakes nationwide, your book will be returned within 3 months time. This is sad but true. But lets say that you do a signing and the store ordered in a crazy number of books thinking that you'll do really well. Even though you may bomb, if you sign the stock of books that the store ordered they cannot return the books! So lets say that the store is stuck with 40 copies of your book. What are they going to do with them all? The bookseller will probably put them on display somewhere to try and get rid of them. This is good for you... especially good if you did this said event at a high profile store with lots of foot traffic. Even if your books don't sell well at first you are getting free exposure! Usually publishers have to pay to have books on display at big bookstores so this is a good thing.
Here's a little story of one of my books being on display: When my book Show Dog came out it was on display in Union Sq in NYC. A very big advertising agency went to the kids' dept looking for an illustrator to illustrate their campaign for an ad campaign for the Bronx Zoo. They saw my book, loved my art and called me up immediately. Even though they didn't get the gig (4 agencies were bidding) I still got paid and it was a fun job. And just the thought that I COULD have had my art on billboards and subways everywhere was very cool.
Good thing number 2 is that if you do a big signing through your publisher the publicist may score you a little write-up in some local magazines or newspapers. I've been in Time Out New York countless times. So once again, even though no one may show up at your event, your name is out there. And the more times you get in something like Time Out New York the more times people will see your name and that's another good thing.
A third good thing is you may do a signing at a small indie shop but this indie shop could have an owner who is plugged in to the publishing world in a big way--think Books of Wonder, etc. Suppose you do a signing and the owner writes a blog for PW or something equally big? You may not sell many books but now you have a new fan and an important one.
So those are a few reasons TO do booksignings. Of course, getting these things to happen can be slim. Really slim. So I still think you should only do them when your calendar is clear and you're mentally prepared for failure. If you can't take sitting there alone and your ego will be permanently bruised then really, don't do a signing. It's not worth the hurt! But if you are brave, try out a few of these options. But you have to strategize to make it work.