Some collages or companies block the access of websites such as facebook or orkut thinking this would distract the students education or the employees work. Some times they have do it to restrict accessing malicious websites which would track the IP address and do their dirty job.
To overcome this problem, we can use proxy websites though which we can access any website and at the same time without disclosing our IP address. And so it ensures our security.
some of the proxy websites I mentioned below.
MY NINJA PROXY