http://en.wikipedia.org/wiki/Dematerialization

In finance and financial law, dematerialization refers to the substitution of paper-form securities by book-entry securities. This phenomenon is ancient, since in many small firms that cannot afford printing secured paper-form securities, the securities are often held in a book-entry form, under the control of an attorney who acts as a notary to certify the existence of the securities, as well as their authenticity. Today, dematerialization concerns more and more listed companies in the US (where the process has begun in the sixties) and now in the European Union, where dematerialized securities represent often more than 99% of the securities listed on regulated markets.[1] However, this recent phenomena of dematerialization of securities issued by large firms is mostly undertaken via Central Securities Depository, a national or regional institution holding the notary function, such as the DTC in the US, which itself entrusts banks and investment firms to act as intermediaries between issuers and investors for the custody of these securities. Therefore, dematerialized securities are often referred as intermediated securities, in particular by the Unidroit convention on substantive rules for intermediated securities.