Thinking a out the web of trust idea...not that it'd be an answer for everyone, but on the same lines as some people's profiles there is a "recommends" feature where they list certain apps, how about something similar for people?

There are at least 4 people I know on here irl who knows me. When it comes to trading and exchanging, I'd be a lot more confident in an exchange with someone who one of those four knew and could vouch for.