"who will ever go to Facebook to search how to buy some power tool?"

Well, considering many people already have Facebook open pretty much all day... if Facebook decided to add a non-sucky form of search, somewhere in a sidebar of wherever, then nobody would have to "go" to Facebook... the ability to search would be already there. (Traces of that are already showing. Doing a search for X in Facebook shows people and pages as usual, but also a few web results. Nowhere near a threat for "real" search... yet.)

Maybe in a few years people will say, "Why did we ever go to Google to search, when we can do it right here on Facebook?" <0.1 wink>

(Of course, things may be different in work environments... If I worked at an office and had to look something up at Google, that should be OK; having Facebook open all the time, on the other hand, well...)

"the department of water should be concerned because coca cola sells a bazillion cans a day?"

That is exactly the point, Google is not a public utility service, it is for profit. Google should be concerned in the same way Coca Cola is concerned about Pepsi, they dominate a certain market, but a moment of hesitation, and oops, you just lost the young demographic.

When Google appeared, Yahoo ware an empire, Alta vista ruled certain searches, where are they now?

my point is actually the opposite of what you assume.

my point is that facebook does not supersede google. as you assume saying cocacola vs pepsi.

google search superseded yahoo search and altavista search.

coca cola also does not replace DWP mainly because as much as people drink soda instead of water, they will ever hardly cook and bath in it.

so, the article talks about two ways to lure users. but they aren't exclusively.