The first time I get an e-mail from you I don't mind if you include your full name, title, phone number, cell phone number, and fax number, along with your company name, division, department, main phone number, address, and website, and even a logo or two. In fact, I like to get all that information at one time; it's a great way to complete my contact file for you without having to ask for missing pieces. I don’t need to see a message telling me that I should save paper by not printing the message (does anyone really do that?), but I'll let it go the first time you send me e-mail.
After that, all I need is your name and phone number. Your e-mail address is in the message; if needed, I can use it to bring up your contact file.
One of Outlook's underused features is the ability to have multiple signatures. I don't know about other e-mail programs, but I suspect they are similar. I have one signature block with all of my contact information; I use it the first time I make contact with a client or consultant. After that, I rely on Outlook's default "reply" signature, a handy option that seems to be a well-kept secret. My reply signature is just my name and phone number. After initial contact, it's usually all that is needed. Your clients and consultants know who you are, and after just a couple of contacts, anyone else will probably recognize you.
If the automatic reply signature isn't right for the situation, it takes only a couple of seconds to choose a different one. There will be times when you don't send e-mail to someone for a few weeks or more, and the person you are contacting might not remember who you are. When that happens, include your name, company, and phone number. If you serve as an officer or committee member for an organization, create a special signature block for each, so the recipient knows that you're writing on behalf of that organization rather than your employer.
What's the point of all this? One of the great things about e-mail is that it can provide a record of how a decision was made, tracking an entire discussion from first contact through resolution. The problem with bloated signature blocks is that they can expand just a few sentences of real content to fill a couple of pages. The message gets lost in needless text and images.
I realize that my e-mail use may differ from yours. Most of mine is with established clients and consultants, so my default signature is brief. You may be contacting new people every day, or sending mostly "official" messages, and need that corporate image. Regardless, before you click "send", take just a moment and decide what really needs to be in your signature. And if a prepared signature isn't right for the occasion at hand, be ready to strip out or add information as needed.
And please think about that lengthy disclaimer your company wants to use. Does it apply? If you send information that is destined to be re-used, don't tell me that I can't use it. It certainly doesn't apply when you're forwarding the joke you just got.
One more thing - never, ever, do I want to see that you sent a message from your Blackberry, or your iPhone, or whatever really cool gizmo you're using.