Steven Johnson points out three:
1. All Shopping, All the Time. If you’re searching for something that can be sold online, Google’s top results skew very heavily toward stores, and away from general information.
2. Skewed Synonyms. Search for “apple” on Google, and you have to troll through a couple pages of results before you get anything not directly related to Apple Computerand it’s a page promoting a public TV show called Newton’s Apple.
3. Book Learning. Google is beginning to have a subtle, but noticeable effect on research. More and more scholarly publications are putting up their issues in PDF format, which Google indexes as though they were traditional Web pages. But almost no one is publishing entire books online in PDF form. So, when you’re doing research online, Google is implicitly pushing you toward information stored in articles and away from information stored in books.
Johnson’s point: “We’re wrong to think of Google as a pure reference source. It’s closer to a collectively authored op-ed pagefilled with bias, polemics, and a skewed sense of proportionthan an encyclopedia.”