Can Signatures Survive The Digital Age ?

When we think of the declaration of independence, the signature of our founding father John Hancock often comes to mind , more than two ceturies after it's signing , his handwriting is instantly recognisable and his name has even become slang to describe any signature 

a new exhibition at the National Archives in Washington explores the stories behind the famous and little known signatures that have made their mark on history

But electronic methods of communicating , email , twitter , facebook , have more or less replaced the need for pen and ink , most of us today don't even sign cheques , and legal documents are just as valid online as they are in print

So what will histiry make of our email sign offs ? can a text from a mobile reveal anything about the sender?