If your friend is surrounded by non-believers, or possibly others who ridicule or belittle his faith on a regular and continual basis, this would be difficult for him. Also, for someone to change as he did, he might be offered a "carrot" of some kind. The "carrot" can come as a number of different means: a job, money, friends and belonging, backup, lime-light, popularity, even companionship or a love interest.
With the economy as it is, I think some people may be feeling pushed to their limits, and feel abandoned or short-changed. Sometimes I think "burnout" or "overload" is involved, e.g., having to be the poster person for the faith.
The best that we can do is continue to be good examples of the faith.