I have a wide range of friends of Facebook—including many writers who are using the site to market their work. While this isn't wrong in and of itself, some approach the site as their personal direct marketing tool, and do more damage than good.
That's why I wrote this lengthy post at Writer Unboxed:
There you'll find basic principles for using the site beyond socializing with close friends, 5 un-marketing principles, and specific tactics to avoid. I also offer a list of extra-credit reading, from trusted sources, if you want to delve deeper.