I am checking caching of my few sites and found that no of my sites were cached after 30th Nov, so i started checking all the popular sites and i was shocked.. Lots of popular sites were not cached after 30th Nov like Google, facebook, Bing, wordpress... I am looking for the reason over network.. Also, i found few of the sites were cached on nov11/12 out of 100 sites what i checked.
Don't worry about this. Google has more than one cache! The public cache display (which is annoyingly buggy) is not what Google itself sees. The "missing" cache file does not affect Google rankings negatively (or positively, for that matter!). What you should worry about is whether your pages are indexed, as opposed to publicly cached. Search for a unique phrase from your page in quotation marks. Did it come up in the results? Then you have nothing to worry about.
You should not be bothered about cache date, if you've not made any changes to your websites. Sometimes Google doesn't display the updated date if it doesn't found any changes. If you really want to test it and then try making some change in your website and then check if Google shows you new cache or now