Merci. Interesting. However ...
I updated my Shockwave Flash plugin to 17.0.0.134 3 days ago.
Even though I rarely allow activation of Flash Player, I did the other day for a specific website and only for that occasion. There may in fact have been some residue left behind.
Since I cleared my browser cache and restarted my iMac, I've had no further problem with browser allocation (as far as I can tell after searching my diagnostic logs).
But back to the original concern: Would zero size buffer allocation be something to be concerned about?