have ISPs cut off high bandwidth connections from those suspected of spamming? can anyone say privacy nightmare?
Yes, absolutely have ISPs cut those off who are suspected of spamming however you don't have to invade privacy to see that something is amiss - if I'm an ISP, I don't need to read an email on the wire to know that a computer that's leased an address from my residential customer pool is spewing outbound port 25 traffic and that what they're saying probably says "V1@g ra"; a mail server and a client look very different in terms of network behavior. If I'm sending out a ton of spam, I look like a mail server. How many computers on residential customer networks of ISPs send out hundreds of messages per minute/hour/day? How many legitimately have a reason for doing so?
This is very, very easy to monitor, from a network behavior standpoint. Your ISP certainly knows how to blackhole DNS/redirect traffic (or switch your cable modem into a private network) to one of their own web servers ("Your account needs to be set up - please contact Comcast", etc.), so it's a trivial task to block suspected spammers and redirect them to a site informing them of how to remediate the issue and regain network access.
There are a few areas in which ISPs need to step up. spam is one - an annoying one. A bigger one is the issue of spoofing. If even 20% of the routers on the Internet prevented spoofing (packets emanating from their networks with IP address other than that of their network or networks behind them), we'd be much better off (think BotNets). This one is sheer laziness/lack of knowledge on the part of network engineers at ISPs - they make the pipes go, so they're doing their job.
And if that's the overall philosophy of the ISPs, it's very easy to see some of the reasons why we're currently reading emails from Bernardo Gentry that say "allegro methylene topgallant resemblant denmark manservant snowball urethra." I kid you not: "manservant snowball urethra".
Please, ISPs... you fail.