For what it's worth, I just spend two days in a user testing lab, testing this exact issue (among other things). 25-45 years old, all had to had a smart phone, half of them were power users. Roughly 80% knew the hamburger meant "other options are hidden here".
Thanks for sharing the data. Been wondering about this myself.
700 million or so Facebook mobile and app users know what the hamburger means as it was on both, it's probably a safe bet your user will understand it
I totally agree with this sentiment. Designer complain about Google still using a Floppy Disk as the basis of their Save icon (because it is outdated and represent a physical parallel)—I think that ought should be creating new paradigms for icon design and the hamburger icon is a prolific and successful example.
To the original author: I don't think it should become the default on desktop, but I am a fan for mobile.
Bonus link: I am reworking my personal site and currently using a hamburger menu WITH the word Menu. Still experimenting for now: http://andy.is/new/
Interesting to note that New York Times app uses a "Back" arrow to get to the list of section on mobile. I know they've had issues with their hamburger on desktop.
To all that believe most users will understand it, you should be careful making assumptions like that. You'd be surprised how often your intuitions are wrong assuming you're designing for a large general public audience (as these tweets suggest). I have seen in a number of tests where many users didn't know the hamburger and didn't know that a magnifying glass was where you would click to search. They were expecting a field rather than just an icon. I'm not saying this means you shouldn't use these icons, but you should definitely think about it very carefully with your target audience in mind. And if possible, test it.
It represents a list of options, more or less. RIght?
If you're scared of using it, maybe a "house icon" could be a solution too.
Using a label, "Menu" for instance, takes up little space. Is the little gain in space with three horizontal lines really worth it?
On a mobile device, it probably is. The real question is: Is it worth using on the web for desktop browsers?
Having a hamburger menu button on desktop seems like an unnecessary extra step. Space is not a premium on desktop, yet I see more sites trying this. It's perplexing trying to understand why.