In a sense, bandwidth fees for consumer-grade access was already tried, in the form of hourly-billing for dialup access. On a 56.6 modem, bandwidth and time spent on line are fairly synonymous.
Regarding the spam situation and bandwidth fees, though, it won't solve the spam situation, in my opinion. After all, what do the spammers care if someone gets stuck with a big bill? Their email was already sent. All it will do is annoy the home user.
I may add, Time Warner at least is quite proactive about this! A long time ago, I mistakenly had an open relay on my home server. Within days of shutting it down myself (I saw the server getting sluggish, saw it was getting slammed), I got a letter from Time Warner, notifying me that they had received complaints that I was sending spam, suggesting that I install their free A/V software, and call them for help if I needed it.
Of course, ISP's could simply add a transparent proxy on SMTP traffic from consumers' connections, and run it through a spam detector (not a filter, just a detector). If there is a long term trend of high-volume spam activity, get in touch with them and see what's up. Even that will get some people screaming. But it is a heck of a lot more reasonable that expecting everyone to abandon Windows for a *Nix, or some of the other "solutions" that I've seen presented.
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