"In 1981 he said that nobody would ever need more than 640 kilobytes of memory on their personal computers."
Although that is widely reported, he apparently never said it.
As for the spam issue, if he'd had his way the spam issue would have been solved.
Bill's answer to spam was charging for email, can you imagine if your ISP suddenly started billing you for every email that went through their servers, anyone who's computer was being used as a spam bot would suddenly get a very big bill for the millions of spams they send, then they'd make damn sure they had proper malware protection in place...
I do not know if you have seen Bill Gates farewell video, when it shows him cleaning out his Microsoft office contents, loading them into a car, then driving off into the sunset with a fond farewell :O)
Once a businessman, always a businessman perhaps. I know many 'retired' business people, who will never let their reins slack on a company that they started from an acorn, even though they have turned it over to their 'family'. And I suspect Bill Gates is of a similar mould!.