Social networking and consumer-generated content are cornerstones of Travel 2.0. Whether for purely time-starved, or simply voyeuristic reasons, consumers are increasingly turning to tagging, a mashup of both social networking and consumer-generated content, to sift, sort, and share information about travel planning and buying.

Imagine if you could somehow use all of the collective travel planning knowledge of everyone that has gone before you, effectively eliminating all of the dog-eared journals and notebooks, all of the underlined notes in travel guides. Well, this is exactly what is beginning to occur with tagging.

Suppose you are considering going on a trip to Venice. Naturally you start your online travel planning journey by searching online for "travel to Venice Italy," where no less than 19 million page links are returned. Perhaps you refine your search, and begin to visit some of the referenced pages. As you visit these pages, you mark or "tag" them in a process similar to identifying browser favorites. Here's where tagging gets interesting. When you tag a page (e.g., with a service like Del.icio.us, you can annotate the tag with a note or reference, helping you to remind yourself why you tagged the page when you return later. Perhaps you tag a museum with "must visit ... Monet painting," or "hip sushi restaurant." As you go along creating tags, a 'tag cloud' is created, highlighting the areas of interest that your tagging is generating, which can be used as the anchor point for future searching and tagging.

Many of these same tools allow you to organize your tags into specific folders and categories (e.g., wine, food, museums and scooter rentals, for your Venice adventure), so that you can refer to them later (perhaps to decide on which restaurant to actually visit). Del.icio.us calls this collection of tags "bundles," and they form the basis for sharing with others.

The network effect kicks in when you post your tags. The next person who comes along planning a trip to Venice can search for other people's tags of Venice instead of just entering search terms. They discover your tags, and reviews, and sift through information on an order of magnitude faster than starting from scratch. If you are planning a trip in conjunction with a friend or family member, you can invite that person to be a 'buddy' or 'friend' and see your tag collections and cloud so that they can discern if your tags are worth exploring and can help the buddy find that ideal place. In order to make linking more powerful, the number of times others include your tags are tallied as a sort of popularity index.

Another site, Rojo, takes a slightly different approach to tagging. Instead of merely tagging pages, Rojo provides a search feature across RSS-enabled news, syndicated articles (e.g., Tripso, and individual blogging sites (including Flickr images, and video or mobile blogs), to give you access to unfettered reviews and stories about local places at a given travel destination. Again, as you identify relevant travel planning info (e.g., restaurant reviews) you can tag it with descriptions, but you can also rank the content so that others can see not just the quantity of tags, but the perceived value of the tag as well (Rojo calls this feature adding "Mojo" to your tag). Along the way, as you accumulate tags, Rojo attempts to assist your travel planning by recommending additional feeds and tags to collect. Finally, once you have aggregated your tags, you can click one button to create an RSS feed that your friends can subscribe to (a great feature if you are anointed group travel arranger).

Speaking of group travel planning, Triporama, a service specifically designed to make group leisure travel planning easier for friends and family, has also joined the tagging fray. Included in the many useful travel planning features (e.g. calendar coordination) offered by Triporama, their 'bookmarking button' enables any member of the group to tag pages on the fly as they research travel about their upcoming trip, automatically saving them to the group's trip page, thus eliminating the need to send the "check this out" or "maybe we can go here" email.

How do all these sites make money? The same pay-per-click 'ad sense' model as Google, but the difference here is that site visitors are more qualified, as they are already part of a folksonomy. Folksonomy users often discover the tag sets of another user who tends to interpret and tag content in a way that makes sense to them. The result, often, is an immediate and rewarding gain in the user's capacity to find related content. Travel marketers can leverage these sites to increase revenues by matching their services and offerings, via tags, to travel planners through promotional advertising, as well as insuring that their sites can be easily tagged.

Tagging is a relatively new Travel 2.0 phenomenon that is still finding its legs. Although burgeoning, the utility of this service is powerful and quite easy to take advantage of. While only a few sites are mentioned here, there are several others (e.g., general-purpose tools Shadows, Plum, and travel-specific sites Gusto!, and TravBuddy) that are not only supporting tagging, but including collaborative filtering in order to help users sift through other people's tagging efforts for relevance. Some sites that have been previewed to PhoCusWright allow users to tag price searches in addition to content, to fill in even more of the travel planning and buying process.

John Bray is the vice president of advisory services at PhoCusWright Inc., where he leads the strategic consulting and custom research practice.