Spotting fellow forumites can be tricky. Big Chief I-Spy would give you 50 points for some runners....
How about agreeing on a way of advertising ourselves as part of this community? I know T-shirts have been suggested in the past, but as no-one has volunteered to take on production and distribution, why don't we try something simpler?
I recall Stringman having a ribbon tied his bumbag at the Three Peaks; on it, was written something along the lines of "http://forum.fellrunner.org.uk/stringman".
Virtually no expense; washable; weightless; visible.
In short, brilliant. Why don't we all do it? Buy half a metre of (perhaps) orange ribbon and a permanent marker - away you go. If it's a short race and you're not carrying a bumbag, tie it round your vest strap - it won't hurt or chafe.
Of course, not everyone who posts on here wants to be accosted in real life. These people can choose to wear no ribbon at all, or one saying "F$%k Off" or "If You're Reading This Why Don't You Bloody Well Overtake Me".
But for the rest rest of us, it would be a good way of making links and helping to establish new friendships, which IMHO is one of the key purposes of this forum.