I think a lot depends on the area you live in. In my area, ticks are more of a problem than fleas, so I've always used Frontline Plus. Piper did have ear mites when we first brought her home, but my vet still wanted her treated with Frontline, and then used a seperate medication directly in her ears to treat the mites.
ETA: I have never seen my cats attempt to lick the Frontline off of each other (maybe it doesn't taste very good?), but I would think that should be discouraged. I think that's why you apply it between their shoulderblades, so they can't lick it off themselves.