Well, after a lot of drama in the Jailbreaking community, there are now two tools to Jailbreak devices running iOS 4.1. Both use the same bootrom exploit, & would require a hardware change to block (as such it's apparently a "pwned for life" Jailbreak).
http://arstechnica.com/apple/news/20...-for-ios-4.ars
From the Chronic Dev Team, greenpois0n:
http://chronic-dev.org/blog/
http://www.greenpois0n.com/
From Geohot, Limera1n:
http://www.limera1n.com/