Well, I'll just quote the source (DJ Tech Tools website):
In the landscape of promotion, there are now unlimited sites on which you can place material on about your work as a DJ. So when someone asks “what do you do?”, which link do you send them? Many DJs have signatures that look like library cards with 5 different links to Twitter, Soundcloud, Facebook, Myspace and if they are lucky a custom homepage. Since you can’t possible expect people to visit all of your content sites, why not aggregate all of those sources into one single page that is easy to set up and changes as your DJ world grows? Well, fortunately, someone invented a service that does just that. It’s called: “One Sheet” . It does not really host much content except for a big splashy photo and a bio. All of the “assets” that you would want to share like photos, mixes, tour dates come from other internet services that specialize in managing those services. One sheet simply aggregates all of them into a single web presense that you can link to with a single URL. Upload a new mix or tour date and your “homepage” stays updated without a single shred of effort.
The whole idea seem pretty cool because, indeed having all these Facebook, Twitter, Soundcloud, Myspace, Mixcloud, Official websites is getting a little bit ridiculous :)
More info: DJ Tech Tools - Create a Great DJ Website, in Minutes | OneSheet.com