Just a more detailed follow-up on Brian's post (even though it's several months old), since I was looking for the same info, and this was one of the first Google links. I then had to do a further search for the details. :-)
After creating and extruding the text, in the main menu, go to Objects > Deformation > Wrap. In the Objects list, nest the Wrap in the Text. In the Wrap Object window, under the Object tab, change the setting from Cylindrical to Spherical, and adjust the various measurements until the wireframe matches your Sphere. Then in the main menu, go to Objects > Modeling > Boole. Place the Extruded Text Wrap into the Boole.
That worked for me. Thanks, Brian, for putting me on the right path. :-)
My only suggestion would be to save this for last, as the Boolean really slowed down further editing capabilities (by like five to ten times slower).