*shrugs* People tend to forget that hamsters are undomesticated prey animals, and as such tend to be nervous fear-biters. This doesn't mean that they're inherently mean or make poor pets; it means that they need to be approached with all gentleness and caution, and handled on a regular basis to keep them tame.

I've also found that the fancier varieties of hamster (such as mottled Campbell's or long-haired Syrians) tend to have greater behavioural issues due to severe inbreeding. Nearly every long-haired Syrian I've ever owned has been intellectually compromised, and mottled Campbell's lean on the neurotic side. It's because after generations of being kept as laboratory animals, and having God knows what bred into them for research purposes, the majority of hamsters available, at least in the States, are genetically unsound, prone to tumours, diabetes, and neurological disorders such as "flipping" (where the animal compulsively performs backflips, all too common in dwarf hamsters).

...and I'll shut up before I get too terribly boring about my area of expertise (although I'm sure it's probably too late for that).