For companies forced to use older versions of Internet Explorer to access badly-written online apps, the Chrome frame plug-in, which modernised older versions of IE, was a handy option. However, that option won't be available much longer: Google is retiring the product in January 2014.
Quite honestly any company which doesn't have now arrangements in place to allow a modern, HTML5-capable browser to run has bigger problems to grapple with than the retirement of a plug-in. If you have built pointers to Chrome Frame into your existing sites or apps, Google has a developer FAQ covering transition strategies.
Retiring Chrome Frame [Official Google Enterprise Blog]