Age gates and the ESRB: going behind the velvet rope

Sometimes when visiting web sites with mature content (as most of us have), you generally come across some page that warns you of the content of the site and asks you if you are over the age of 17 (or 21), and you have two choices: you can click "yes" and proceed with the site, or "no" and it takes you to some random site like
Yahoo! or Disney.

Obviously a warning like that will not prevent underage kids from seeing the graphic content, but now a new system has been popping up that will prevent those with horrible math skills: an age gate
which has the user input his or her age and then, through some complex algorithms, determines whether or not you are of the appropriate age to view the site. This new system will soon become standard practice, as the ESRB is requiring websites that host game trailers and demos of M-rated games put those files behind an age gate to protect the innocent.
GameCloud has interviewed a number of editorial directors from sites such as IGN and 1up to guage the reaction of the video game press. It is a lengthy, but interesting read.

What do you think of an age gate? Is it simply a inconvenience or a smart move by the industry to show concern for underage game playing?