Google has acquired a lot of ad competitors, but I can't remember any general-purpose search engines. It seemed more like they died out naturally over a long period. I welcome new information if that's not right.
Edit: Per Wiki, Google has also bought and killed the following search engines/services that nobody has heard of: Outride, Kaltix, Plink, Like.com, Orion, Metaweb, Awkan Technologies.
Edit: Per Wiki, Google has also bought and killed the following search engines/services that nobody has heard of: Outride, Kaltix, Plink, Like.com, Orion, Metaweb, Awkan Technologies.