There is an interesting study going on here. Part of the results were presented at 26C3 today.
Basically:
It is easy to assign an arbitrary text to the correct author, if a sufficient amount of known text from the author exists ... probably bad for privacy
Fortunately, it seems to be as easy to obfascate your writing style or even imitates another's style. You can even help building a corpus which should be a basis for a semi-automated style obfuscation tool by participating here.

Basically:
It is easy to assign an arbitrary text to the correct author, if a sufficient amount of known text from the author exists ... probably bad for privacy
Fortunately, it seems to be as easy to obfascate your writing style or even imitates another's style. You can even help building a corpus which should be a basis for a semi-automated style obfuscation tool by participating here.
