sites that allow sharing

-When the internet started some of the early social sites tried to discourage linking to other social sites thinking that they may contain the crowd that goes there. As the internet got older and everyone had more than social site to hang out at, the sites that allowed sharing did very well.
some social sites allowed a stream where you can just about share any link and they became the largest social sites on earth. You see if a site allows links to somewhere theres very likely going to be a link back from that somewhere soon as people like having more than one social site (I know I do)
a point