Facebook is the "trendy" social network and I just look at their "sponsored" groups around travel industry players.

Southwest Airlines on Facebook is leading the way, with a big group.

Here some stats:

Global Size: 47,200 members
Discussion Board displaying 73 discussion topics
The Wall displaying 917 wall posts.

Topic exemples:

Have any funny crew stories?
How many of you compare prices before choosing Southwest?
Do you think Southwest Airlines Should add international routes?
Best flight crew ever
by being involved with this site can we get more deals? ;-)
Have you ever been in a plane crash? o-[

Other Facebook Sponsored Travel groups

Contiki
Global Size: 37,130 members

STA Travel
Global Size: 20,979 members

Travelzoo | Travel Deals
Global Size: 1,009 members

Some other players

Restaurants, cooking chef,... have their groups and built their communication with Facebook network.

Also some Travel 2.0 players, give some application for Facebook users.
See TripWiser, SideStep, TripAdvisor and others...

So what do you think, Facebook the "trendy" network for travel industry players?

Give us some others exemples.