This is how I understand the whole Vaseline/bacteria thing (in a semi-medical opinion):

Petroleum based products such as Vaseline should be avoided as a lubricant, not only because they deteriorate the condom, but also because they are anhydrous, meaning they contain no water. Anhydrous products can seal in potentially harmful bacteria causing infection and owies (okay, owies isn't a medical term).

Thats just how I nut it out anywho