How exactly did the US feds "Seize" 5 million in bitcoin? I thought the whole point was that it wasn't seizable unless you got the encryption keys, which would be weird since MTGOX is based in Japan, no?
Presumably, if they wanted to seize bitcoin, they'd produce a demand to turn the bitcoin over along with stating the legal authority for the demand and the legal consequences of failing to comply with it; lots of actual seizures work that way.
But if you read the article, the $5+ million seized from Mt.Gox by the US government was US dollars (not bitcoins) ($2.9 million from Mt.Gox's account with Dwolla, and $2.1+ million from two Wells Fargo accounts), so "how can you seize bitcoins" is irrelevant.