What happened with my Orkut account when I leave it sign -in ? Be cautious.

I do regularly explore the internet through my office but In my office some sites are blocked for suring like Orkut, Job sites and Porn sites. I have created a profile in orkut. Last week i have went to a cybercafe to send a resume through Naukri.com then i also checked my Orkut account and unluckily I forget to unclick the checkbox “ Remember me on this computer” and after some time light went out and i came back to my home.
One day after one of friend told me that at night I was through orkut but I told him that i did not log into my orkut that day.
After three days , i had visited the site and my entire profile was changed and there are some very wrong words added into my profile and this suy who used my profile already sent some very wrong messages to my friends. This was very ridiculous.
Then after, I have updated my profile once again. Please do take care of your account when you are surfing on net and do not forget to signout from your any account, otherwise it can be misused by anybody and you can faced the very occurred situation like me and if you are surfing from any common place , then never click on the check box “ Remember me on this computer”.
All the best and happy surfing............