Just what the world needs, another social network
And in a style that reeks of a domain trying hard to be cool, it's at so.cl (apparently, it's pronounced "Social". Thanks for figuring it out, Bing, that saves me a lot of hassle)
Coverage at VentureBeat. Some say it's just an old site being relaunched.
(I don't know if I remember it correctly but if you have a company in Chile with a specific name you can require anyone to hand over the .cl domain using that company name. There doesn't seem to be a company called SO in Chile so there may be an opportunity here for someone to acquire the so.cl domain pretty cheaply simply by starting a new company in Chile . If Bing don't hand over the name you could get some fair publicity for your case - "Bing accused of cybersquatting". Either way, you win.)