Barack Obama's inauguration was the second most-watched in history, with an average of 37.8 million total viewers tuning in Tuesday. Only Ronald Reagan's first inaugural in 1981 had a bigger audience, with 41.8 million, according to Nielsen Media Research. The No. 3 inaugural was the 1977 swearing-in for Jimmy Carter (34.1 million). The least-watched was George W. Bush's second inaugural in 2005 (15.5 million). Nielsen provides statistics for inaugurations dating back to 1969 http://latimesblogs.latimes.com/showtracker/2009/01/barack-obamas-i.html
It's 2009. http://www.cnn.com/2009/TECH/01/21/inauguration.online.video/ Find me the numbers on this from 1981.
The internet wasn't available in 1981 like it is today. But yes, that is interesting that so many people watched Obama's inauguration online. If you add that to the number of people that watched it on TV, maybe Obama's inauguration was the most-watched in US history.
I think those numbers just show how many people use the internet for video now, and not a reflection of the enthusiasm for Reagan vs. Obama. The hospital I work in had to send multiple emails to all of the employees to basically find a damn TV because the network was crawling, which sometimes impacts patient care.