Today's Webmaster Help video from Google is interesting. It tackles hidden text, but not the kind that Google has always spoken out agains (and talks about in its quality guidelines), but a more legitimate kind.
In the video, Matt Cutts answers the following submitted question:
How does Google treat hidden content which becomes visible when clicking a button? Does it look spammy if most of the text is in such a section? (e.g. simple page to buy something and "show details" button which reveals a lot of information about it).
"I wouldn't be overly concerned about this, but let's talk through the different consequences," begins Cutts. "It's pretty common on the web for people to want to be able to say, 'Click here,' and then 'show manufacturer details,' 'show specifications,' 'show reviews,' and that's a pretty normal idiom at this point. It's not deceptive. Nobody's trying to be manipulative. It's easy to see that this is text that's intended for users, and so as long as you're doing that, I really wouldn't be too stressed out."
He continues, "Now certainly if you were using a tiny little button that users can't see, and there's like six pages of text buried in there, and it's not intended for users, and it's keyword-stuffing, then that is something that we could possibly consider hidden text or probably would consider hidden text, but in general, if you just have something where you have a nice AJAXy sort of site, and things get revealed, and you're trying to keep things clean, that's not the sort of thing that's going to be on the top of our list to worry about because there's a lot of different sites that really do that."
"It's pretty common on the web, and a lot of people expect that on the web," he says. "Take, for example, Wikipedia on your mobile phone - they'll have different sections, and then if you click, they expand those sections, and there's good usability reasons for doing that, so as long as you're not trying to stuff something in in a hidden way that's deceptive or trying to distort the rankings - as long as you're just doing that for users, I think you'll be in good shape."
As a user notes in the comments of the video, you have to click a button to reveal the video description on YouTube.