Personally, I like the <eighty-subdomains>.BigCompany.COM. approach;
it just scales better. Less messy. Tastes great.
I once asked Vint why they'd been allowed to call it InternetMCI.COM rather
than Internet.MCI.COM and he said "the sales and marketing people were more
powerful than I was" or words to that effect.
Recall my previous article about "dot envy".