Would you be upset, should I be?

The internet kinda of make things tougher than it use to be when buying a part. Few years ago at the Don Garlits swap meet/car show, I was waliking by a vendor that was talking to a guy about a 400 block and 440 steel crank (451), The block had the mains cut already to fit the 440 crank. What stopped me in my tracks is when he tells the guy $175.00! I wanted to jump and say I"LL TAKE IT! But that wouldn't be the right thing to do, so I waited and was hoping he wouldn't buy it. So I wait, and when I hear the buyer say, "Well I'll think about it, " and says Thanks and walked away. He hadn't cleared the vendors area by a couple of feet, When I told him, I'll take it! And I did. The block had been cleaned and new cam bearings, freeze plugs and painted! What a deal!
Now here comes the internet and this site and others like this. Some people think an inquiry should hold an item till they say no, while others are sending PM's trying to buy it from under the original posters, others are making offers for less than the seller wants. Still others ask you to hold it till their hunch back brother straightens up and they'll have the money. I think after dealing with this and watching others. The best approach is to lay down your course of action in the For Sale ad, First come first sale or I will not hold this item, no trades, Pay Pal with or without PP fee's , Money order Only, ETC.