Selling isn't for everyone. Most transactions most of the time go fine. Some do not, and you do have to be prepared to take some losses.
It doesn't matter where you sell. If you sell most places online (and certainly Amazon, eBay, and anywhere you take PayPal), you're subject to their buyer protection policies which mean that you take returns and all those risks. If you sell in your own brick and mortar stores, you have shoplifters and kid damage and credit card chargebacks. If you sell on Craigslist you risk mugging and wasting a lot of time. If you sell only online through obscure venues accepting only postal money orders, you risk not selling much.
Like the news, the information you get here is skewed: generally, if it bleeds it leads so if someone has a bad situation, it gets posted here. The majority, the good or uneventful ones, don't.