Cold and straight out, "He who snoozes, loses." People ask questions all the time and never take action. People will make offers and then not act on it--- "will you take $X for it?" Some people respond by PM or email and the others never see the correspondence.
I go by the time on the communication on "I'll take it" offers and expect payment in 12-24 hours, then I go to the next in line.
It's not eBay, or Nordstrom's, and mistakes will be made. There are some flakes out there too, although I would say that is a tiny fraction compared to eBay, or Craig's List (flake central). My impression is that everyone here is doing the best they can.
Expecting action in a couple hours is unrealistic. There are people who have limited access to email and work for living, and have *lives*, so an offer made at 7AM can't be acted on until after dinner, etc.
I do think it would be flakey if someone jumped in with a higher offer and the seller took that over a commitment that was already made. While I don't think it is unscrupulous, "best offer" posts are a problem waiting to happen.
What is important to me is that people represent the condition of their offerings honestly and well-- and ship promptly.
If someone gets the item first, you have to take a win-a-few, lose-a-few attitude. We're trading toys here, not life-critical items. Stuff happens.