Finally, a Facebook application that makes sense. A new online travel portal is trying to alleviate the biggest obstacle people have in renting out their second homes: their fear of renting to strangers.

Portland-based SecondPorch.com has launched a Facebook app called "Rent & Trade Vacation Homes," which, it says, is the first "socially enabled" vacation home site that allows vacationers and vacation home owners to connect.

The site integrates with Facebook's wall stream messaging and allows "friends" to discover who on their Facebook account has a home they are willing to rent out. Vacation home rentals is the fastest-growing segment of the lodging industry -- a $50 billion a year industry at that.

Second Porch users can search for homes based on budget, location, amenities, recommendations and -- most importantly -- relationship to the owner.

In what is clearly a sign of the economic times, 45% of the Second Porch home owners have opted in for trading their homes with others. The site's founder, Brent Hieggelke, knows first-hand about rental horror stories. His father rented out his vacation home to a group that used it to host a bachelor party. Damage tally: $4,000.