This is old news but talk of Google’s Public DNS brought up this bit of data:

Marissa ran an experiment where Google increased the number of search results to thirty. Traffic and revenue from Google searchers in the experimental group dropped by 20%.

Ouch. Why? Why, when users had asked for this, did they seem to hate it?

After a bit of looking, Marissa explained that they found an uncontrolled variable. The page with 10 results took .4 seconds to generate. The page with 30 results took .9 seconds.

Half a second delay caused a 20% drop in traffic. Half a second delay killed user satisfaction.

Just a friendly reminder that computers are not pure syntax manipulators; they are embodied systems with complex non-formal behavior to which we are highly sensitive.