Post count might not be an absolute but it does help... Mandatory images would help, along with many other things that would help but are not a guarantee....
Bottom line is it's up to the buyer (who is spending their hard earned money) to check things out and take the risk...
Thats why I posted the how to buy on eBay FAQ... How many eBay buyers do you think follow that FAQ? Not many... images, images, images.... Check IMEI, PIN, ect.....
I do think a minimum post count and mandatory images would help....
This FAQ should also apply to purchases from ANY forum...
Buying a BlackBerry off eBay - BlackBerryFAQ
Kris