There was an interesting post in Language Log today, and Language Hat refers to it as well. They are talking about the use of the Oxford comma and why it often is necessary. This was the sentence in question:

quote:

Traders and fund managers got huge rewards for speculating with other people's money, but when they failed the parent company, the client and ultimately the taxpayer had to pay the bill.

. For the meaning of the sentence, they needed a post adjunct and Oxford comma.

Indeed. My company is always removing my Oxford commas, and I now I have some ammunition. That post adjunct comma is even more necessary here, though.

When it aids clarity, commas are needed. I'd say Pullum is dead on in this. I'll go further and suggest that when the pace - the fluidity - of a sentence is improved, a comma is beneficial.