very tricky area, and has become worse since I first started using the net and forums.
I'm with Crackle in attitude on this one, though I accept our attitudes aren't always realistic. I consider CC my cycling home on the web and I have a golf home, on the web, as well. They almost become extended families for me and, as such, I dislike the facility, and the goodwill, being abused. I've also been known to send stuff on the basis of 'pay me if you're happy', never yet been let down on that one. I'd also rather give stuff away to younger members than have it gathering dust in the garage or go to the hassle of trying to make a couple of quid on e-bay. I haven't built up that much cycling stuff yet, but you'd be amazed at how much golf stuff has been given away over the years.
As I tend to take part in things, ie actually turn up and ride a bike/play golf, buying and selling becomes self policing. As a rule I deal with people that I've met or that are known to another I've met. If you get involved it's surprising how broad a circle of contacts this gives you.
A good example is the book raffle, I have read on, passed it on, and am awaiting the arrival of my second book.