Travel is the new fashion, it seems, judging by the number of websites jumping into the space lately. Today Groupon became the latest site to strike out into the discounted travel space with Groupon Getaways (a partnership with Expedia).

After Gilt and Hautelook demonstrated near immediate success with the daily fashion sale model, it seemed a new company following the exact same model appeared every week faster than you could say 70% off. Gilt was the first of those sites to bring travel deals into the mix with their Jetsetter website; but today there’s the American Express backed Vacationist and Exclusively.in (a Gilt style site targeted towards Indian fashion and design), who recently expanded to include Asian focused travel deals.

Unlike fashion, there’s no Vente Privee (who American Express also recently partnered with) – that is an established behemoth who’s been making money off the model for a while. That’s the good news, now the critical look.

While startups like Airbnb are having success as an un-hotel travel coordinator for the value conscious, we do have to wonder if discount travel will eventually run into some of the same issues of discount fashion: luxury fashion sales bounced back, brands got smarter about manufacturing which means less inventory to discount in the first place and a focus on full priced sales. Make no mistake, while Gilt and others continue to do brisk business in discounted apparel, the leading US flash retailer is looking for growth in retail at regular price.

According to Pegasus, a hotel reservation system provider used by 90,000 hotels around the world, hotels in the US and around the world are seeing growth in spite of regional crises.

“March global bookings and revenue reached the second highest growth pace over the last twelve month period, increasing by +10.8% and +15.5%, respectively, over prior year.” {the Pegasus View March 2011}

While we have no doubt that Groupon’s massive audience will buy into the travel deals, and those seeking travel deals will buy into Groupon’s regular offerings, we wonder how long it will be before the same discounted dates are bouncing around on the various sites. What’s wrong with that? Limited inventory plus three different options for filling it means that the discounts may get to be less attractive over time.

The one advantage Groupon may have though is their international reach. Groupon Getwaways is starting in the US, then Canada with an international rollout after that. Unlike fashion, in addition to there not being a clear behemoth there aren’t any sites outside the US who’ve successfully developed travel flash sales.

In fashion the private sale space is pretty crowded, with companies like Gilt, Rue La La, Hautelook and Ideeli among many others prompting questions about the sustainability of the luxury sample sale model past a certain point. Even though most of the sites have offered household items and other non-fashion sales, Gilt was one of the first to establish separate destination sites for different markets. Gilt Fuse offered a destination for mass market brands, Gilt Man split off the guy focused offerings and Jetsetter became the first site to apply the online private sale model solely to travel.

The move was seen as a smart one for a way to increase revenue amid concerns over limited quantities of unsold designer goods. Vacationist only marks the second site to focus on the travel market – compare that to more than 10 sites who battle it out for unsold apparel, but we have to wonder if the same issues will come into play.

The recession hit almost every consumer sector, and hotel bookings sank in line with consumer demand, so many hoteliers were willing to offer discounts to fill empty rooms. Though the economy is still not completely out of the woods, there have been signs of spending in some areas picking up. Starwood Hotels, the group that operates 4 and 5 star hotel chains like W, Sheraton, Le Meridien and St. Regis, reports a pickup in occupancy rates for the first quarter of the year and rates beginning to rise this month. {Reuters}

Expedia has also reported an increase in worldwide hotel revenue, even though the per room rates are down 5%. {WSJ} Though bookings may have been helped by discounts, special promotions and other offers to fill more rooms, once occupancy begins to increase it’s not a stretch to assume that hotels will offer less substantial discounts as they try to return to more solid growth.

Unlike clothing, where a designer can use lower cost fabrics and less costly detailing to bring prices down for discount collections, hotels don’t have the same options. Sure, they can take away the continental breakfast that comes with a rack rate or charge extra for amenities based on the rate type, but the person who cleans the rooms are paid the same regardless of if you’ve booked at full price or a discount and many other operating expenses stay the same.

So while the discounts on sites like Jetsetter, Vacationist, or even old favorites like Priceline and Hotwire will still be there, as things get back to normal don’t count on them being as deep or available as often.