How can I control a list of applications in "Share" pop up in Android built in browser?
This list is generated (on every boot) from the installed apps that have registered themselves with the system to handle this function.  The only certain way to remove an entry from this list is to  uninstall the corresponding app.

You can try de-compiling the app, removing the share intent from its "manifest.xml" file, and re-packing it.  However, this will most likely cause issues with Market updates because of signature mismatches.