Thank you for more well-supported ideas.
The TalkPhysics team will shortly be looking at this whole issue, not least as an attempt to minimise spamming. It was felt that a major possible advantage of TalkPhysics over email discussion lists is the knowledge of who you are addressing.
We had begun from a logic of requesting a minimum of information at registration to encourage users to register, but we are likely to start by more information compulsory at start-up.
We may well develop something like your last idea with tagging – that just as we will shortly have groups and resources with tags and being able to search them, we should be able to extend the idea to users. This will need to be a later stage. I’m not sure whether we’ll reach the “mouse-over” idea – I would also like to see this on the Dashboard, but is technically difficult.