I would argue for changing your definitions as follows:

> Untraceability means that nobody is able to trace back your actions to your unique online account.

> Anonymity means that nobody is able to determine the real identity of the owner of the online account.

Another example is a Bitcoin transaction. A Bitcoin transaction occurs between two accounts that are each essentially identified by highly unique number:

 - The transaction provides excellent anonymity as people only know the keys and not the identity of who owns them.
 - On the other hand, all actions related to an account are purposefully highly traceable as all transactions are recorded in a public ledger. 

This is essentially the opposite of the voting example given by [Stephane][1] where there is untraceability but not anonymity.

  [1]: http://security.stackexchange.com/a/74032/9668