it is not like you can have 2 values for a single bit at the same time.. and density is so high these days that it makes sense to have a single write wipe the previous data forever.

It exists already, it is called a routing registry. The most famous is RADB but they can use IRRd to have their own private version (which they probably do already).

It does if you can justify the need to Google, for now they have quotas (see http://code.google.com/intl/fr/appengine/articles/quotas.html).

AppEngine quotas explained

Feasible, algo is described here:
http://blog.fireeye.com/research/2008/11/technical-details-of-srizbis-domain-generation-algorithm.html

AFAIK they do, Bell business customers aren't affected. Wholesalers could be considered as business, as well as their own business customers.