While answering and commenting on another question I discovered that I am apparently thinking about anonymity differently than everyone else who responded. There are two questions stemming from that discussion, this is the first:
What words can fill the gap in this sentence?
[Word] is anonymous.
The examples I seem to find acceptable:
The writer is anonymous.
The paper was anonymous.
The call was anonymous.
Should I be saying:
The paper was written anonymously.
The call was made anonymously.