It's not uncommon to see businesses on .ORG, or organizations on .COM. Since the major TLDs currently have no restrictions on registrations, almost any type of site can exist on a on almost any of TLD. Why have your webSITE be on .COM or .ORG, when you can have it on .SITE? .SITE will provide much needed clarity and consistency to the current convolution in the domain name space.
When can I get my .SITE?
The new gTLD applications are still being reviewed. The earliest you can expect for any of the new gTLDs to be available is in the spring of 2013.