Leonard Lin jotted down a list of facilities web frameworks aren't yet providing: Infrastructure for modern web sites, divided into user-visible (comments, tagging, chat), and foundational (sharding, counters, bucket testing). It's interesting to read his inventory, because at Tabblo, I'd say we've tackled about 30-40% of each list.
Like any product, web frameworks have to decide what audience they'll cater to. Watching Django's progress, it's clear that the tension is between helping new users get on board and helping the advanced users scale up their sites to handle success. As an example, consider database schema migration. A number of the solutions being built are working hard to let developers avoid writing SQL for migrations. This is an on-boarding feature.
In our database schema tools at work, what we're grappling with now is how to carefully arrange upgrades so that the servers are offline as little as possible. Some database changes can be made before the new code is running (create table), some can be made after the new code is running (drop table), and some have to be made while the server is offline (rename column). It's tricky to get right, but important if you want to maximize server availability. This is a scaling-up issue.
Web frameworks can become more successful by adding either kind of feature. More on-boarding features will grow the usage of the framework, but may mean more people get to the point of needing scaling-up features, and get frustrated. More scaling-up features will satisfy the big sites, but may make the framework harder for the newbies to get their heads around. In the end, both are needed.
Jacob Kaplan-Moss commented on Leonard's post arguing that implementations of items on the list will be so site-specific, that so much domain knowledge will creep in, that there won't be much to share, and so adding them to web frameworks may not be practical. That may be true for some items (sharding), but not for others (counters).
In any case, it's a good manifesto for the things people have to build on top of web frameworks like Django, and are built over and over for each site. It'll be interesting to see what parts can be provided as general-purpose solutions.