Ryan Singel on why corporations put 400 words of legal BS at the end of every email:

But the ominous warnings that you must obliterate, incinerate, and forget any email not intended for you don’t actually mean anything, according to legal experts.

and:

In a trade secrets case, for instance, the absence of a notice could be used to argue that the sender didn’t care about keeping the content under wraps.

There are edge cases where notices matters in court, but most of the time those legal notices only serve to waste bandwidth.