I'm more worried that airlines are pulling out from sites like expedia.
I tend to do a search on expedia etc to give me info on who goes from A - B with prices, then I check the individual airlines websites for any special deals and things such as baggage allowance and menus.
I imagine a lot of people do the same but equally a lot will just book with what is on expedia etc and in that case AA loose out.
You know when I looked at flights for my trip to NYC, AA didn't figure at all in my mind whereas UA, DL, CO did.
I end to do the same as tonty does, I also do the same with hotels though - or most other products I'm thinking of buying. Afraid I never assume any one site will be better than any other and often going directly to the site (airline, hotel, car hire) is the best deal anyway...