… give an answer. Please.
One of the most frustrating experiences of editors is asking someone to referee a paper or a book manuscript and getting no answer. Occasionally, this is because an email is sent to the wrong address or gets lost. But that’s not the typical case. I also know everyone is busy and even answering a simple email takes time.
The problem is that when someone doesn’t answer, there is no obvious time frame for deciding when to give up and ask someone else. Meanwhile, precious time is lost for both the editor and–more importantly–the author.
An especially obnoxious case is people who ask for time to think about whether to accept the assignment and then still give no answer.
Do the right thing: if you don’t have time or desire to referee something, just say no. But say something.