OpenTable is just a machine. Obviously it does not know the rhythms of the restaurant, it's just a tool.
Let's say the restaurant DOES release all its tables into the software (which no one does for all the very good reasons mentioned upthread). Calling the restaurant and speaking with a human who is actually there on, say, a Saturday night at 8 PM, and knows from experience that a little bit of overbooking might make up for cancellations, no-shows, etc., is still going to produce a better result. The human will be able to override the parameters that we set into OpenTable for covers per half hour, turn times, party sizes, and all that fun stuff.
OpenTable is a wonderful tool for a lot of things, sure, but it still doesn't beat a good maitre d at seating a room

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