An e-mail from Gillian Carson telling me and other attendees of the Future of Online Advertising conference (June 7 and 8 in New York City) that the event will be Wi-Fi ready reminded me of my preference for pen and paper to take notes.
As a matter of etiquette, I find it rude towards the speaker to be paying attention to her/him only in passing between checking e-mail, websites and whatever else you feel like being distracted by.
I noticed a lot of that happening while I was at South by Southwest.

If you find the session or speaker boring you can always step out and wait for next topic.
My suggestion is, at such events, close your laptop and open your ears.
It is perfectly fine to use your toy during breaks.
It might be better though to interact with other humans and make new connections.

Worth reading on the topic of Laptops, Attention Deficit Disorder and Speakers: Boon or Curse? (Ben Buchanan), Is anyone listening? WiFi and the new ADD (Jeffrey Veen), Notebooks for Conferences (Felipe Gaucho) and Conference Dynamics (Heather Green).

I previously wrote about Twitter, Blackberries and the Age of Constant Interruptions