Alexis Madigral weighs the pros and cons of Google Instant, which displays search results as you type. Here are "two pretty glaring downsides":
First, it is a visually intense experience, possibly even an overwhelming one. Tech journalist John Pavlus described it as "like having a websearch seizure. [The] screen explodes with noise as you type." Second -- and this is more subtle -- I worry that Google is driving more traffic to the most statistically probable searches. The most-trafficked ways of searching for something will get more trafficked. I wouldn't be surprised to see the number of unique searches drop because people see something in the list that makes sense, even if it's not exactly how they'd have put it.
The feature is spreading to Twitter, YouTube, and iTunes. Alexis in earlier post addresses Google's "Odd Vision for the Future of Search." Jason Newman "present[s] to you the full power of Google Instant via the most obvious song: Billy Joel's 'We Didn't Start the Fire.'"