I sell on Bonanza, other sites, as well as our own website. Bonanza has been a good venue, and business has been picking up. They have increased their business by 128% from 2013! It's been a couple of years with them, easy venue to work with. As with any website, see if the store you're buying from is professional, see how many transactions there are, and check on feedback. If you want professional service, look for sellers that have a good professional web presence, and understands what customer service entails. An occasional or part time seller may not be as responsive. If they offer Paypal or Amazon as a payment option, you do have protection. Same thing if you are using a credit card. Use their services if you need to, when the seller doesn't respond.
Be aware though, that sometimes merchandize can get lost or damaged in transit, or the seller may have a temporary glitch in his supply chain. Talk it over, chill... Not everyone is trying to scam you, most sellers are trying to grow a business, not take your $50 and run. I am surprised to read the rants here from buyers, because of the protections out there for them, they shouldn't be out any money at all. Learn the rules of the road, don't send cash or money orders, use instruments that offer you protection, and jump in.