I'm with the majority but...
Yes Guy should have just made a mental note to do a better job of housekeeping his account, apologised to those whose messages were bounced, and got on with his life.
However, those who have said that GMail should delete messages from the server after downloading to the user's mail client have missed the point. GMail actually has no fewer than three options of what to do when messages are collected via POP3: delete the GMail copy, archive the message, keep the message in the inbox, or delete the message. It's up to the user which action to take.
Archiving my messages gives me the best of both worlds: a local copy when I'm at my PC and a nice searchable archive that I can access from anywhere. I can even do this on my mobile phone, using Google's nice Java mobile client. Who needs a Blackberry?
People who use a free service need to accept that if it's worth more than the money being paid (i.e. nothing) that's a bonus. Despite its quirks, GMail is considerably better than many paid-for services so that's a very big bonus. Why they offer POP3 access at all is beyond me, as it undermines their advertising revenue, but I'm grateful that they do.
As others have said, demanding that Google introduce a feature that will benefit only the tiny proportion of users who use POP3, and have filled their mailboxes, while increasing the disincentive to view ads is ludicrous. However, making a modest suggestion, which they are free to ignore, would not be an unreasonable thing to do.
If any professional person, least of all an IT journalist, admitted to using Hotmail, or any of the other free webmail services for essential business purposes, he'd be laughed at with some justification. Why should expectations of GMail be any different?
Google may be an arrogant, even sinister, mega-corporation but if this article is the best its critics can do, its position seems pretty secure!