Not an answer to your question, I'm afraid, but I'm firmly of the opinion that increasing Mathematica's reach in market X and field Y is strictly beyond the scope of this site. Such a joint undertaking on this site (if it were to happen) would also be complicated by the fact that user A and user B probably won't agree on the same X and Y.
This is solely WRI's responsibility, and they were fairly late to the game and introduced some much needed statistics/probability functionality only in version 7 and expanded in version 8. Same is the case with image processing functionality. In contrast, MathWorks has had statistical and image processing toolboxes (among several others) available for quite some time now. If you look at these facts, it's a no brainer as to why the adoption rates for Mathematica are so low — most people have had to roll their own, which is not fun when there's a reasonable and easy to use alternative that packages it all for you.
With that said, there is something that you (or someone else) can do (and the community can aid):
- Create packages/applications that aid the use of Mathematica in market X/field Y and release it to the world (or at least, the community here). I guess these will need to be fairly robust if it's going to be used by several people of varying expertise in Mathematica. Respond to bug reports and feature requests quickly to encourage people to support it.
- Make use of the community promotion ads (which shows your ad on the main page) and get users interested.
- Write a book on how to use Mathematica for X (again, use the ads if you don't benefit commercially)
Eventually, if it is good, it'll gain the acceptance of users, who'll then probably convince someone using MATLAB/R to switch (it'll be a while before that happens for statistics/analytics, but it could be faster), who'll then... you get the idea.