Lost Dogs trading etiquette suggestions

I'm slightly annoyed, as this has happened a few times now, and it's starting to get to me. I started a thread asking a question about vinyl that had nothing to do with asking for anything. Someone just happened to pm me and say "hey, just pay me the shipping and it's yours!". WOW. how generous! Totally unsolicited! Then they pm me a bit later saying they lost my address, as the vinyl is ready to go. Fine. Just give me your paypal address and let me know how much shipping is.

PM again. No answer. Wait a week. PM again. Still no answer. I know they are reading them, as they are in my sent folder. Totally dark. :?

Rewind about 6 months ago. I'm in search of DITP vinyl. Someone pm'd me and offered it up, saying they'd contact me after the Christmas holidays. Nothing. No answer to multiple pm's over several weeks.

I have NO issue with someone backing out of a deal. I did it myself once, and compensated the individual for their time, which I'm not even asking for from these individuals. I'm just asking for the courtesy of not wasting my time. Tell me if you are backing out of your offer. Even if you are offering something for free, and then you change your mind. I don't care. I will respect your honesty.

JUST PLEASE BE UPFRONT ABOUT YOUR INTENTIONS, and maybe think before you offer something up that you might not be prepared to sell/trade/give.

thank you for your time,

Paul