I.e. Google must be top-of-mind competitively for any web startup.
The new awareness derives mainly from the plight of Kiko, a web 2.0 calendar app / company that went under after Google released Google Calendar.
To paraphrase some famous words of Larry Ellison, Google can cut off the oxygen of many startups. Of course, to be fair, Google created a lot of that O2 in the first place.
Here are some areas / companies Google could threaten next:
Zillow et al. Ever wonder why the only place not using Google Maps for Real Estate is Google? It's an ad business, you know.
Obviously Apple and Yahoo have this, and Google can't ignore that Music was the spark behind the one site they envy: MySpace.
That's Second Life and anything with an Avatar in it. Anyone recall that MSFT has bought up Lionhead (xbox RPGs), Rare, and Massive (in-game ads) in the last 6months? Google could build their own and/or buy up a bunch of the top games and shove 'em together..
Digg. Not that Yahoo has succeeded at this, but it's certainly something that Google could do well. Digg was recently dubbed "The world's slowest site" by Philipp Lenssen. It's funny 'cause it's true. Could Google do it better? (That was rhetorical).
Of course the startups are not defenseless. Their primary advantage is that organizationally, Google is a gangly overgrown teenager, with all of the focus and attention span that implies. And Google ain't getting any smaller or faster.