M&A (mergers and acquisitions) are once again flourishing, driving a new wave dot-com boom. We don't have quite the "irrational exuberance" of the 1990's, but hey, $1.6 billion for a site that hosts home videos of people lip-syncing is plenty irrational and plenty exuberant.
In addition to the Google/YouTube affair, other recent romances include News Corp/MySpace, Adobe/Macromedia, Microsoft/Groove, and many others. And like the 90's, I think the business plan of many of these companies is simply to get acquired. They demonstrate just enough technology and sizzle to attract attention and wham, the lawyers from some big company or other are down on them like flies on ... well, you get the idea.
And it's all about the Web. For YouTube and MySpace (I think the next big one will have to be TheirWhatever), it was branded sites for people with too much free time to hang out. In the case of Macromedia and Groove, it was leading technology for building Web sites or for sharing data on the Web.
So basically, billions and billions are being spent so that people who sit in cubicles and drive around in cars and walk around with cell phones and iPods in their ears and live in separate houses or apartments can sit in front of their computers and interact with each other.