This means that you can discover interesting things from thousands of people, not just a single small network.
Rummble works with your smart phone, which also then allows you to take a photograph of something to share at once on Twitter, Facebook and other usual suspects. Their archive goes back to January 2007, so they've obviously been around a while. I've not tried it myself, but the interface screenshots look nice and clear (nice to see the geolocation shots are UK based as well!) Having looked at the team page I'm assuming that they are a London based organisation, which is a nice change, and (exploring the site as I type) their London office is at Clerkenwell Road.
They certainly seem to have a following - there's a live Twitter feed for mentions, and it was ticking over nicely while I was on the site. They have a few friendly quotes from Mashable, TechCrunch and The Guardian as well (but guys - you need to add in the links to the reviews as well, so we can read the rest of the good stuff!)
So, if you're looking to try out one of these services, and want to do something a little bit different, give it a go. Especially if you're UK based - give some love to the UK resources!
Bottom line: interesting twist on the concept, brownie points for flexibility, adaptability and friendliness!