In Quora's case the text blurring applies both to search engines and users. I've visited the site as the googlebot user agent and it is exactly the same as what non-logged in users see. They also aren't doing any tricks to hide the full response in the HTML.
Also FYI, most major search engines have "secret" IPs from which they crawl websites using normal user agents (ex: Chrome, Firefox, etc). They then compare the results to the results from their main crawlers to detect the type of cloaking you referred to.
> I've visited the site as the googlebot user agent and it is exactly the same as what non-logged in users see
.. except, of course, that the googlebot just reads the HTML. The CSS3 blur only causes problems when you try to read the site visually, via a browser.
> They also aren't doing any tricks to hide the full response in the HTML.
Yes, that's why the googlebot can read it.
I don't know why you're bothering to argue that this isn't cloaking. It most assuredly is.
I guess I should be clearer. The full responses aren't in the HTML at all. The blur effect is just images. Neither you or google see the full responses
Quora may be blurring things for both googlebot and users but it still does not excuse the fact that they are deliberately obscuring content for non-logged in users. So in this respect, they are no better than expertsexchange except maybe a less unfortunate name.
Also FYI, most major search engines have "secret" IPs from which they crawl websites using normal user agents (ex: Chrome, Firefox, etc). They then compare the results to the results from their main crawlers to detect the type of cloaking you referred to.