It's definitely a fear for me. I noticed that often when I "buy" things i give the seller money, take the thing i want, and then they never give back my money.
I fear that if I "buy" an optical drive, something similarly dreadful will happen. I guess for things like food and clothes it's not as scary since I at least get to keep something useful (knock on wood). But with an optical drive, if they don't give me back the money, then they may as well have thrown a giant chunk of wood at me. What am i supposed to do with a giant chunk of wood, knock on it?