Now, consider adding a URL to every signature. Lets even use your URL, which is 35 characters long (and lets not even count the NULL or length byte). Adding this URL to 30000 signatures would add 1050000 bytes, or just over 1MB. This is an increase in 12% of the keyrings!
Yes, but we have to assume that the need for central key servers would go away if we had a way of distributing the data around, which would reduce the problem substantially...
On the other hand, using my method and your "URL" (clark.net) would add only 10 bytes per sig, or 300k. This is only a 4% increase.
The current PGP keyring model does not scale anyway. Suppose one day every user on the Internet will have a key... It is not relevant whether the space per key is 100 bytes, 1000 bytes, or 10000 bytes. All of these sizes are small enough for it to be quick to transfer a single key. There will soon be no way to transfer and store the entire key ring. In the long run, the problem must be solved using an entirely different, distributed architecture. Tatu