UK ISP Virgin.net has responded to continued broadband ADSL service degradation by not only preventing new subscriptions, but also introducing an NTL style usage cap of 1Gb per day / 5Gb per week (aren't there 7 days in a week?). The ISP has also acknowledged the on-going dialup problems:

Virgin.net have contacted a proportion of their broadband customers and requested that they reduce their usage to a maximum of 1gigabyte per day and 5 gigabytes per week. (This is enough to surf approximately 40,000 Internet pages and collect approximately 10,000 emails each day).

Virgin.net's first obligation is to our existing broadband customers and these two measures should ensure a significant improvement in broadband service performance.
Please bear with us whilst these measures take effect.

To date less than a handful of UK ISPs have felt the need to adopt usage limits and not all offer such low flexibility (1Gb). It'll be interesting to see how customers react, especially since it's not an abnormally cheap service (fairly standard price point).

Regarding the unmetered dialup difficulties, Virgin.net states:

Our engineers are still working to resolve this issue. However, this fault should only affect a small number of customers on the 24Seven package.

We are currently experiencing difficulties with the Virgin.net 24Seven service. We are trying to resolve the problem as soon as possible and apologise for any inconvenience caused.

We note a distinct lack of detail, but at least customers aren't being told it's their fault anymore.