If you're citing a personal correspondence, e.g.:
"Cats are vicious" (Bill Bobson, personal correspondence, March 12, 2012)
and you continue to use this personal correspondence with a cat expert, do you refer to them simply as Bobson, or Bill Bobson?
Continuously referring to personal correspondence sounds like a bad idea… if many parts of the discussion come from unpublished comments from your correspondent, he should probably be a co-author rather than simply cited. Otherwise, you can quote the personal correspondence once and explain its context at first point of use. Something like:
Many of ideas developed in this paragraph were inspired by a series of discussion with cat expert Bill Bobson, over the spring of 2002. In particular, he drew our attention to the viciousness of cats and their unwillingness to comply to their master's will.
In addition to @F'x' good points, depending on the nature of the communication, if it is "preservable" (an email, a PDF, or a conversation for which you have a transcript) it may merit a bibliographic entry [Bobson~2012] or Bobson (2012) depending on your style. Certainly do give a date or dates, and the disposition of the records, such as they may be. That is, as in other situations, being honest and helpful to the reader is a good guide.
I think every style is going to be different. APA doesn't add it to the references at the end. It also only uses initials and not the full name in text. Additional reference to the same communication would still include the initials.
The key thing to remember is to be consistent and let the copy editor enfore the style rule. Nobody is going to reject your work because of slight stylistic deviations,
