To see who was a member of several different groups, you can combine their membership lists into one and search against that.

	cat Fitness_Galaxy AAA United_MileagePlus | grep "John Smith"

If you only want to see the number of matches, you can use grep's -c option (the c must be lowercase):

	cat Fitness_Galaxy AAA United_MileagePlus | grep -c "John Smith"

Or you can pipe the result to 'wc -l':

	cat Fitness_Galaxy AAA United_MileagePlus | grep "John Smith" | wc -l