From what I've read, ami, I've seen people use forums with sections for doms and subs to find each other. Never used it myself, so I can't comment on the safety (before you do, very much make sure you read up on safety and follow all the precautions), but I imagine it's an effective way to find like-minded people to form more of a relationship and emotional power trade with compared to a brief session at the local dungeon now and then. Some dom-sub relationships form out of existing 'vanilla' relationships, so it can work even if you have or look for a relationship with someone who is open to the idea.