Somehow we're privy to a tip. And following our keen intuition (or greed), we bypass other sound investments and go straight into buying shares in a tiny, unprofitable company that might cure cancer, revolutionize eBusiness, or harvest cheese from the moon. It's possible, of course, to make a killing with this company. It's also possible that our investment gets killed instead.

Bottom line? Be careful. The truth is, many companies––even ones with a good idea––come and go. (And when they go, so goes your investment.) So do-it-yourselfers need to be careful about hot tips from friends and family, impassioned calls from unfamiliar brokers, and information that can be bent, biased, or bogus.