Regardless of precautions that websites use to protect their participants, anyone with the proper equipment (Protocol Analyzer) can capture the traffic on a specific IP address, trace it to its origin, then do a search and locate that person. If anyone wants to catch you, and they have the proper resources, they can.
Not quite. The analyzer has to be set up in a location where the traffic passes, and there's no simple way to associate an IP address with a particular person, unless you have access to his ISP's internal billing records.