Not quite. It's just a broken tracking system. I guess you could do this trick to make some poor blogger think he just got 723459288 new subscribers overnight, but you can't actually cause him to have that many.
I'm curious if inflating your RSS subscriber number gains you any significant amount of extra subscribers. My guess is no.<p>Might help when selling RSS ads I guess.
I don't think FeedBurner can fix this, short of not counting aggregators that incorrectly report subscriber numbers (like NetVibes is doing in this case).