Most corporate IT departments are trying to ensure only a small approved set of application is used. I have even see a company that runs a big internet site, trying to ban 500+ engineers from downloading free stuff from the internet, was pretty funny and show how out of touch some IT departments are with the need of the users.
An alternative approach would be to understand the reasons behind the popularity of these “rogue” applications. Needs drive demand. Organisation work hard on understanding the needs of their customers, why not try to understand the IT needs of the internal users.
Imagine a day you start a new job and you get a laptop loaded with useful tools and bookmarks to on-line serviced used, it would be a big step from the common practice of a standard set of Microsoft Office suite programmes.