Google Instant will impact the way people conduct their searches, and that will lead to repercussions for the search ecosystem. Steve Rubel says that it'll make "Search Engine Optimization (SEO) — the dark magic that helps websites appear higher in search results — totally irrelevant."
Matt Cutts, weighed in on how he thinks things will change:
I've said it before, but SEO is in many ways about change. The best SEOs recognize, adapt, and even flourish when changes happen.
Q.Will Google Instant change search engine optimization?
A.I think over time it might. The search results will remain same for a query, but it's possible that people will learn to search differently over time.
Q.I don't like Instant! I'm turning it off!
A.We provide option right next to search box, but I'd encourage to spend some time with it first before you've a knee jerk reaction. As Google Instant page mentions, "If everyone uses Google Instant globally, we estimate this'll save more than 3.5 billion seconds a day. That's 11 hours saved every second." With over a billion searches a day and over a billion users searching each week, that adds up to 350 million hours of user time saved a year. That's 500+ human lifespans saved a year by this feature if everyone used it.