[QUOTE= I personally never knew smearing vaseline on your back would cause your fist to continually bash someones' face in.

I'm going to make sure I try that next time.[/QUOTE]
That's not the point. Vaseline is a lubricant, which I'm sure you know from experience, and could play a role when you need grip. And most BJJ people (Bj bread and butter) will tell you, that it's hard to grab someone when and perform a choke/submission when their all sweaty. Hence why most people will train with and without the gi.