It was recently suggested to me that I create a Facebook page for my company as Facebook has more users than Google.
That, by itself, is not a reason to create Facebook presence. For example, if someone wants to research me or my company, they would do a search on a search engine, not Facebook. Typically Facebook is not used for research.
If you are a consumer goods company, you could use your Facebook page to offer discounts, send out announcements, and otherwise connect with your customers.
If you are a political candidate or political cause, you definitely need a Facebook page. In general, I think that Facebook is an excellent tool for non-profits.
A software company might want to use Facebook to run their user group community, although I don't think it would be the best choice.
But for a small PR agency, a Facebook page just does not make sense.
Just because a tool exists, does not mean you should use it.
Jim Horton has written great surveys of corporate use of Facebook and Linked In. He notes that most corporations are failing to integrate their use of social media, that is, link to their Twitter feeds and blogs from their Facebook and/or Linked In page. He also shares my view that it is not necessary for a corporation to have a site on either network.