To the hobbyist or african cichlid enthusiast, a hybrid is practically worthless: unpredictable behavior with high potential to foil any breeding plans in the tank (i.e. having socolofi/elongatus hybrids in the same tank with pure socolofi and elongatus will, by default, make any fry born in that tank suspect).
To the uninitiated novice, however, hybrids are just another pretty fish.
Highly recommended NOT to bred OR disseminate hybrid fry in any event as hybrids will only produce more hybrids (which really aren't need in the hobby).
In regards to most mbuna's in assorted tanks being hybrids, that all depends. Many LFS' use those tanks to consolidate mbuna's (they'll get auratus, kenyi, red zebras, ps. elongatus, acei, yellow labs, labeotropheus, and even venustus, etc, then lump them all in the same tank instead of setting up separate species tanks for them).
However if the LFS orders (or acquires) hybrid mbuna's, they'll also be added into the SAME tank. Some may be stocked with mostly hybrids (maybe the known species previously in the tank sold, and only hybrids remain for sale).
You have to know your fish and basically know what to look physically for. You want to select the fish that clearly looks like a red zebra than sort of looks like one (and "looks like one" means more than just 'being orange').