It does sometimes. I have told people to hold parts for me while I can plan a road trip to pick them up. In a few cases other members tried to buy the parts out from under me, even offering more money than the original poster was asking. Lucky for me the sellers had some integrity and held the parts for me. I really appreciated the sellers doing that. I will send them a deposit in the mean time for them to hold for me if they require to hold the parts. Some guys refuse and still hold the parts for me.
I have also made a point to hold to my word. If I tell someone that I want the parts, I get the money orders out usually the next day sometimes two. Ask any of the sellers that I have done business multiple times. Once I tell them that I'll take it, they usually have a money order in their hands within 2-3 postal business days. This way the sellers trust me and do not sell the parts out from under me. Check out my feedback score - over 40 and all positive.