There is no reason to avoid buying a guitar on eBay. The only trick is to deal with reputable sellers, but the eBay feedback makes this easy. I don't sell on eBay directly, but one of our families close friends sells many guitars online, probably close to 100 a year. He has impeccable feedback, which he has developed very carefully over the years he has been doing this. He is honest to a fault in his auctions, and this is why he has such great feedback. When I do feel the need to sell a guitar on eBay, I have him consign it for me, and pay him a 10% consigners fee, specifically because of his feedback. He sells VERY high end guitar this way, and no one has ever complained about doing business with him on eBay.
Stick to sellers with great feedback, and your eBay experiences will be just fine.
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"Cowards can never be moral."
M.K. Gandhi