Google Instant changes everything. Despite the assurances of Google product managers and engineers that Google's ad business will remain relatively unaffected by the company's new focus on real-time search results, observers outside the company are convinced that delivering search results as the user types will have a significant impact on Internet advertising.

Google Instant returns search results with each character the user types, search results that correspond to the company's prediction of the most likely query for those characters. This means users will be exposed to multiple sets of search results, particularly if they type slowly.

Whether the changes are positive or negative, both for Google and its advertising customers, remains to be seen.

"Google is changing things at a pretty central part of the last second of the user interaction," said Horst Joepen, CEO of Searchmetrics, a search analytics company. "The jury is still out on whether this will be a positive for Google at the end of the day, or whether they will step on their toes."

Matt Cutts, the head of Google's Web spam team and a frequent blogger on search topics, published a blog post on Wednesday to allay fears that Google Instant will make search engine optimization -- SEO, what ad firms do to increase Web site visibility to search engines -- irrelevant.

Cutts suggests that Google Instant will lead to broader querying without much extra work, though he concedes this will inevitably bring changes to SEO, changes underway since Google began emphasizing personalization in 2007.

Joepen foresees Google Instant driving advertisers toward the most costly search phrases or keywords. He suggests that Google Instant will promote "short tail" keywords -- broad terms -- over "long tail" keywords -- specific terms. That could increase the price of broad search terms.

"This really will create a problem for complicated search phrases," said Joepen. "If Google distracts me before I finish typing, is that really what I wanted?"

That's not really a problem for Google, however. It's an opportunity. Higher keyword prices mean more ad revenue.

The impact of Google Instant may be even more meaningful in the mobile arena, where users don't want to do a lot of typing. Google Instant for mobile is expected to arrive in a few months.