xMarks has an amazing set of data. A set of tagged bookmarks on a large enough scale is essentially like running mechanical turk (with 2,000,000 users) on the entire internet (better yet, only bookmark-worthy parts of the internet), and asking it to "describe this page in 10 words or less". The results, I think, are the most accurate description of URLs you could get on such a large scale. Essentially every site that has over a certain amount of bookmarks is <i>guaranteed</i> to be of high quality and very relevant to what it's been tagged as. (The only problem is when sites change, domains expire, etc).<p>When I was making MoreOf.It, I scouted the competition in depth. The only one that stood out was xMarks, and similarity search wasn't even their main gig. They understand the richness of bookmarking data. They've separated URLs into categories, and have the highest ranking sites in those categories. They also nailed similarity pretty well. I might even say their results are better than mine, because they have a much larger index of sites.<p>Two and a half years ago, when I first built a prototype of similarity search, there were hardly <i>any</i> meta-websites. Besides Quantcast and their ilk, and bookmarking websites, and maybe a couple of bullshit "site worth calculators" (which just multiply site traffic by an estimated CPM), there was hardly anything happening in the meta-site space. Now, there are tons more services that cater to people Gooling an actual url or site name. To name a few, CrunchBase, AboutUs.org, BackType, UberVU, SimilarSites, SitesLike, and sites that aggregate results from these (QuarkBase). "Meta" is blossoming, and it seems like xMarks could take advantage of this with their rich dataset.<p>For example, as someone told me I should do, they could sell analytics information to websites about their competitors. If you're ZipCar.com, for example, you would pay to know the following: How have people described zipcar.com in the last (x amount of time), and what are the trends of those tags? How is my popularity vs. an automatically generated list of my competitors [ala: similar sites]. Which competitors are trending, and with which tags? Any new competitors that are breaking through the ranks? Some information could give cues to alter your business: What types of tags are related to my business are trending right now (i.e.: perhaps "bike share" is becoming more and more popular. I think that's valuable information. And, like an arms dealer, you can deal to both sides of competition. With 2,000,000 users organizing this set of data (for their own benefit of course), it's pretty confident sample size and it's win-win for everyone.<p>Frankly, I don't understand what benefits "synchronizing" offers. Why not just store your bookmarks on any number of bookmarking websites (Delicious, Google, etc), and then log-in to that website from whatever browser/computer/device you want? I do, however, see value in the analytics of what people bookmark, and how they bookmark it.