I do sell mining contracts on ebay and other areas, but *always* with hardware available to back the contract up. In auctions, I always start a auction with no reserve and run from my 100% positive feedback account. My contracts always mine on the customers pool and not my own, and my contracts always include the full debug output of the stratum mining proxy as proof of submission. Cant really say fairer than that.
Any person selling a mining contract who refuses to allow the buyer to select their own pool is probably not worth buying from IMHO.
I do agree with other posters, some of these contracts look like speculation or people trying to recoup money already paid out for pre-orders. I have seen a few ebay auctions promising:
http://jerome.blogs.lincoln.ac.uk/files/2010/07/ludicrousspeed.pngbut only when they "take delivery" in 2014 (saw one recently for 100TH/sec! LOL). Some of these auctions even name their ASIC suppliers and in most cases the 'supplier' is a known scammer. So either people who got scammed trying to get some money back, or people who genuinely believe these units will ship (poor gullible..)
The prices of mining contracts at GHs exchanges and other hosted solutions is, in my view, ridiculous - sometimes tens of thousands of dollars for hashing speed that you could buy hardware and run at home for around 2 to 4 BTC. Its no wonder there is a market for contracts on ebay/others for people who want to play fair, believe in BTC and who want to help the network. But sadly, that condition also means there is a market on ebay for scammers too.
Agree with the previous poster - even if I sold a 24hr 50GHS contract for as little as $20 the purchaser wont recoup that with today's difficulty and exchange rate (~$5 loss). But people do still buy. Perhaps its the joy of the luck of the block discovery - much akin to the rewards of gambling I suppose. Perhaps its the belief in the long term future of BTC. Who knows individuals reasons, but all I know is they do buy the contracts.
For my history, Ive been mining on and off since 2009 - from CPU days, through GPU days and now to ASICs - mainly solo - so I like to think I know a thing or two about this game, even if it has taken me till 2013 to come out of lurk mode on bitcointalk.
Hope this insight helped
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