Safecoin handles it in this way:

"A separate persona, the TransactionManager, is proposed to handle all the token-related transactions. A TransactionManager group will be a trusted group of nodes which are closest to any given transaction identity. ... The PUT request for safecoin is "no duplication allowed", i.e. if there is already a safecoin data having same name (first 32 bits), the new put request shall be rejected." -- http://maidsafe.net/SystemDocs/user_perspective/safecoin.html

The part "trusted group of nodes" sounds shaky. Coins using a block chain are trustless. My idea of a currency without a block chain is that it should be trustless. It could however be that "trusted group of nodes" is a trust based on cryptography or something like that. Then Safecoin is trustless too.