Is the "Finite Blockchain" idea secure? http://www.bitfreak.info/files/pp2p-ccmbc-rev1.pdf


  This paper will describe the way in which these three mechanisms can
  work together to form a system which provides a high level of
  integrity and security, yet is much slimmer than all other purely P2P
  currencies. It also offers other potential benefits such as faster
  transactions and lower fees, quicker network synchronization, support
  for high levels of traffic, more  block space for custom messages, and
  increased anonymity


Has anyone analyzed the design and found it to be secure? My own primitive analysis didn't find any weaknesses, but I'm no cryptographer or security expert.
The most apparent weakness is the following: If an attacker has enough hashpower to build an alternative branch starting with the current block, and to be ahead of the network once that block is pruned; he can rewrite the entire history completely, assigning bitcoins arbitrarily among the addresses he chooses.

This can be alleviated with archive nodes which are consulted in times of emergency.