Dynamic limit on the block size.

Proposed raising the maximum block size in steps to 6 MB, then letting it grow further with sustained demand.

Phase 1 set the limit at 2 MB, then 4 MB, then 6 MB. In phase 2 it would rise by 10% whenever three-quarters of blocks over about four weeks were at least 60% full, and it could never fall. It aimed to balance low fees against the risk of mining becoming centralised.