I'm pretty sure outbidding or buying a coin on another member's list is bound to happen. Especially with all the members bidding on CNG and looking on eBay. One way to think about it is there is always more out there, hopefully at around the same price.
I've bid and won against members here. I've also purchased a fixed price offering someone asked about. My general policy is that I won't bid or buy if I wasn't already considering it before I saw their post but if it's already on my list I'm still going to go for it.