I usualy use finger style alone when I play classic guitar (nylon strings) , and rarely with elec ... If you play elec , you'll definately need a pick for executing a lot of techniques ... Also you can't shred with your fingers on an elec cuz the string spacing are too small.
Anyway, there ain't no rules... Look at Mark Knopfler (Dire Straits) , he's a cool elec guitarist who only use finger picking... I usualy play his stuff with finger picking to emulate his sound and feeling.
