Email Signatures

I have always wondered why people bother to put their email addresses in the email signature that's attached to every outgoing email they send. I mean, isn't it enough that whoever you sent it to already knows your email address from the "FROM" detail?

Another thing that annoys me is the disclaimer that they always attach on corporate emails. Don't they know nobody fucking cares about that let alone read it seriously? The unnecessary text just makes the file get bigger and bigger through each reply... your friggin eatin up my valuable email space