Facebook says it owns rights to the name 'book' (chicagobreakingbusiness.com)
recommended by 1 user | 2010 | 21 points by blahedo | big tech | original thread |
One user recommended this thread. What they said:
scott_s Sep 25, 2010 | on: Got a cease-to-exist from eBay for owning a domain with… | context

You should read this entire thread about "TeachBook," which was sued by Facebook: http://news.ycombinator.com/item?id=1633106

In particular, tptacek's comments about PerfumeBay are relevant to your situation.

Short version: yes, you should be worried. Even if you are in the clear, legally, you may have to deal with the legal system itself. Being legally vindicated can still be expensive.