Another option for this idea, instead of outsourcing it, is to create essetially the "last.fm" of travel...collect information from people about their trips (where they stayed, how they got there, where they visited) and then when people want to plan new trips, you can intelligently recommend things using the collected data as a reference.

The hard part would be collecting that initial data. Maybe a Facebook App would encourage people to participate.

I picture the trip planning screen being a set of sliders and drop downs. Put in where you're starting from, where you're going, how much you want to spend, and then the site does all the work.