The idea of suggesting possible searches in a drop-down box while a user types is far from unique to Amazon.com. But the Seattle-based online retailer appears to be alone, so far, in being hit with a patent infringement lawsuit over the technology.

MasterObjects, a San Francisco-based tech company, filed the suit earlier this week, citing a patent received in July 2010 for a “system and method for utilizing asynchronous client server objects.”

The patent covers “A session-based client-server asynchronous information search and retrieval system for sending character-by-character or multi-character strings of data to an intelligent server, that can be configured to immediately analyze the lengthening string and return to the client increasingly appropriate search information.”

No word yet on why MasterObjects singled out Amazon, as opposed to Google or Microsoft, or anyone else. We’ve contacted Amazon for comment and will update this post depending on the response.

Via TechCrunch and PriorSmart.com, which both have copies of the complaint.

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