Pleading the 5th

[Anonymous]

In light of recent "situations" involving cpunks and the courts, I've been 
thinking about the 5th Amendment.

I pose two questions:

If called to testify in a criminal case, and asked the question "Are you 
known by any other names" (or a derivative of that question), could one 
plead the fifth in order to prevent the disclosure of a pseudonym?

If asked the question "have you ever communicated with [third party]", 
could one plead the fifth if that communication was made through a 
pseudonym, and tying that pseudonym to oneself could potentially be 
incriminating?