I played around with this for work and fonts appear to be the biggest culprit of selling you out. User Agents can be somewhat unique depending on what you've installed that may have modified them, but fonts are far worse. From what I gather, the flash app returns the fonts in installed ordered and not alphabetical. So unless your system is factory fresh, it may still be distinguishable from someone else with the exact same setup, provided you installed any fonts (or apps w/included fonts) in a different order.
For me it is plugins. I only have a couple installed in chrome, but apparently there are also system-wide plugins that it is picking up info on. 19.68+ bits of info based on plugins alone.
