Basically you know how there's a suggested amount to bid? Don't bid more than the suggested amount! If you do, you're losing money for yourself and other people who bid.

However, sometimes it can be a bit hard to predict. In the time it takes you to make a bid, there may be many others who also make a bid which means your bid goes over the limit, thus making everyone lose money. This happened to me twice today which is why this @marketstack guy is so upset.