I agree with the argument but am also beginning to be convinced by the opposing argument for many cases.. Consider 37signals' products, they don't have the product name in the verbatim .com form for any that I see - they've had to append words on the end. Apple doesn't own MacBook.com. Even companies who own their product names as domains (e.g. Fogbugz.com) aren't necessarily using them as a primary URL. It seems customers/users aren't /that/ fazed by it.
The fact that companies are doing it doesn't mean that customers aren't fazed by it. Sure, 37signals is doing well, but do you think the "hq" part of the basecamp domain helped? When 37signals weren't that well-known and wanted to market it, how many potential customers do you think they lost because people typed "basecamp.com", didn't go where they intended to and never visited again?
Customer retention is like trying to plug all the holes in a sieve, and a bad domain is one more hole. Personally, I'd gladly pay $50/yr for a domain if it meant that suddenly the squatters went out of business.
I can't find fault with your arguments because I'm sure they're true for many cases (and the 'plugging the holes' is entirely valid).
That said, my gut feeling is that at least a plurality of people are Googling terms like 'basecamp' rather than typing them in as URLs. And I doubt that those who do type in URLs are fickle enough to write off the task on one failure. Proving it either way would be laborious (but would make for interesting research).
I always try to subtly correct that, it irks me when misspelt :P I'm sure people will google for things (hell, I have the "I'm feeling lucky" shortcut bound to "l" on my browser so I do "l basecamp" and I'm there), but this only works if you're first on Google for your name, which isn't something many companies can boast, and certainly not when they're just starting out, which is the time you want new customers the most...
I can personally attest to becoming very confused by having the add "hq" to basecamp's address. It took me a very long while to get accustomed to that URL, having to repeatedly google basecamp to find it.
