Starting out getting an invitation, there's actually a orkut invite pool on google groups. So the people who want an Orkut account are likely going to have to use the google groups service in order to be invited. Already it seems kind of silly. Ask around how to even get into Orkut before you can start using the services.
Once in the signup is pretty simple. You fillout forms upon forms. You find communities then you chat your life away s'craping the persons page.
The hacking communities are stuffed full of ignorant people posting about hacking yahoo and hotmail emails. A bunch of people try to social engineer each other into getting passwords. Most people don't know much about actual programming, but want to be taught how to make exploitive advanced code.
The most appealing part is the communities, which has events listed and works mostly as a forum. It seems more a simple extension of google groups.
There's plenty of exceptions, always, and anywhere, but for the most part orkut is an unmoderated mess of spammers and unmoderated idiot kids spouting off stupidities over and over again.
I tried to give computer advice a few times and I was contacted by Yahoo! messenger multiple times from people asking me to join their "crews" or yahoo! group on hacking/cracking.
There's nothing to distinguish Orkut. Post your picks, big deal. Nothing new, nothing interesting, and the worst part is, unmoderated.