While I agree with you that there is a couple other things to consider. The ICANN agreement requires the contact information to be valid. If the contact information is not valid, then the registrant is in violation of that agreement and the domain name is subject to termination.
In the case I mentioned, everything except the e-mail address was correct. It seems a bit extreme to terminate a domain when 95% of the info is correct and there's no reason to think the bad address was deliberate. I don't see any obviously correct solution to this problem. I'd like to say that if the email bounces, the registrar has to try to contact the registrant using the other info to tell them to fix it, but that has its own problems. Due to all the fake renewal notices from places like DRoA, the registrant is as likely as not to throw away mailed notices, and registrars would argue that for $8/yr, they can't afford to send mail nor to deal with the phone calls. R's, John