It doesn’t make much sense: According to Valleywag, Microsoft is in “advanced discussions” with lifecasting startup Ustream.tv for more than $50 million.

Why would the venerable Microsoft want upstart Ustream now, particularly with the whole Yahoo! purchase thing going on? Valleywag says Microsoft would use Ustream “as a way to promote its Adobe Flash competitor, Silverlight.”

Again, we ask why?

But when you take a closer look at what Ustream has been doing lately, it makes more sense for a major buyer like Microsoft to become involved. Ustream is more into eventcasting than lifecasting these days, and eventcasting has greater potential in the long run.

Lifecasting is sort of hit or miss, with people broadcasting their lives 24/7 for all to see. Sometimes you find interesting people, but most of the time their lives are pretty dull.

Eventcasting, on the other hand, has much more promise because it allows viewers to tune into special events that they would not normally have access to — these events might not be covered by traditional or new media.

Ustream, which claims to broadcast 5,000 hours of video daily with 300 broadcasts taking place at any given time, has streamed several concerts, including some from tween sensation Hannah Montana, singer-songwriter James Blunt, the Plain White Ts. and Soulja Boy.

Of particular relevance is Mitt Romney and Gov. Mike Huckabee using Ustream to reach potential voters in the U.S. presidential race. Romney just dropped out of the running, while Huckabee is still in the hunt.

“We are certainly focused on eventcasting,” Ustream CEO Chuck Wallace told NewTeeVee. “We have a great platform and we welcome everybody, but our focus is certainly on these deeper events.”

For the record, Wallace and Microsoft both denied comment. Wallace said the company is in the middle of raising its Series A round of financing but is open to offers.

Who knows. If the Microsoft-Yahoo! deal goes south, the Redmond boys might snatch up Ustream, a bargain at only $50 million.