We too have been on Facebook, Twitter and TripAdvisor. It is a great way to gain a wider "fan" base and spread the word.
For every clinent that comes out with us and then posts pictures/comments about their own experience on their own page, that then goes on to potentially 100's of freinds.
We also encourage clients to "like" our page and to post pictures & comments
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The only downside, is that you must keep updating and making sure that questions or comments are dealt with promptly, but thats business