"...And of course, most popular aggregators don't care, today." I see this as analogous to browsers accepting almost any old garbage as HTML. When a browser parses the HTML it knows that there are errors but ignores them. It is because of this that 99% of pages that haven't explicitly been through a validator are broken in some way.
In the same way, aggregators know when a feed is bad but don't complain. If the aggregators marked the bad feeds with an un-smiley face which linked to a validation service then the people who made the bad feeds might be shamed into fixing them as everyone in the communinity can see that it is broken.
Originally posted as a comment regarding Computerworld's RSS feeds that don't validate
Posted by stuartcw at November 15, 2002 04:25 PM