I agree with Paul and george about the despicable scum. Ahem...I mean lawyers, LOL!
But I will also add a new one: real estate agents. Beyond using the web for listings, they are some of the most technologically inept folks I've run into! And I have spent 20 years in technology! In fact, most agents really only went to the web with some decent amount of enthusiasm once there was reasonably simple CMS platforms available.
The only tech that a large number adopted quite readily was email ;)).