Even when BOTH parties do their best to be fair and honest, what runs great to one person may not be acceptable to another. I liken it to lending money to a family member, its so easy for hard feeling's or misunderstandings to happen and things can go sour/south very quickly.
Even fleaBay is not without risks. One example is, I bought a BRAND NEW con-cor DL-109 from a 100% pos FB seller. The listing said it was tested before listing and it "ran good". When it arrived, it ran like CRAP! I emailed the seller about the problem and s/he assured me it had in fact been test run and was perfect.
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Thinking something came loose or something got out of alignment during shipping I opened it up to try and find the problem. What I found was both front and rear powered truck had not one but TWO pieces of flash between gear teeth causing most of the very poor running. It was a manufacturing /quality control issue and could never have run properly even before it left the factory.
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I filed a complaint, but the seller was not about to do anything to make it even half fair. Since I really wanted that specific loco and had invested a lot of time into fixing the problems, I decided to keep it instead of returning it at MY EXPENSE, which meant I would be out dollars in addition to my time invested and repair. I tried giving the seller an out, being s/he may have simply forgot to test this specific loco, to no avail. Lesson learned, I have NEVER since bid on anything that seller put of on ebay again.
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The world is full of LOCOs (non RR type). I had a Chicago corp exec buy a film scanner from me, used it to do a Christmas present/ favor for another family member and decided to return it. When it arrived back it was a mess with crap all over it and other non-shipping damage.
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In another case I sold a nice microscope on eBay. The buyer decided the scope was defective and wanted a partial refund to cover new objective lenses. I KNEW the optics were great so I investigated the issue. I found him BOASTING about how his new microscope (he bought from me) was so great in is business. He even posted MY copyrighted photo on HIS web page boasting how great the scope was. I ended up using HIS boasting about the scope on his sight to beat his eBay complaint AND forced him to remove MY photo from his web page.
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The world is a mixed bag, I sold a nice Mamiya MF SLR and a like new Nikon to collectors in Japan & Switzerland and no problems what-so-ever, in fact both were very happy with their respective cameras. (plus I was able to by a scooter so I could get out and about more).
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I have seen some very trivial things happen (and I do mean trivial!) in web based social media of many flavors, turn into major PROBLEMS very quickly, and once that happens things never seem to quite return to normal again. The prospect of hard feelings and tarnished reputations are REAL, and often over the tinniest most insignificant of things. On other web sites, I have seen great people I knew, leave and never return, while the problem maker remained...
JD