if the optical drive can't receive it for whatever reason then the dinky 2MB flies by
If the computer is unable to transfer data from the physical system memory to the drive, then you've got bigger problems on your hands (like, for example, PIO mode)
in alcohol 120 i've seen the buffer drop in 10 seconds and scratch a disc, and the buffer was 128mb...so i believe the buffer on the actual unit is extremely important
Sure, a larger hardware buffer could help you a little bit. But at high 16x DVD burning speeds, this will amount to roughly 300 ms of extra protection. What's an extra 300 ms to compared to 10 seconds? Big hardware buffers are more or less snake oil, and the only place where they are remotely useful is in standalones where a large system memory buffer is not available.