If Wal-Mart started selling discs of their own production, a bunch of us would go down and check them out wouldn't we? Now granted, we've been around the sport and we would know better (probably just by looking at them but for sure by handling them). You talk to others and they then understand. That's the way this sport works: word of mouth, you talking to the other guy that was out playing by himself and you joined him. If Nike wants to jump in and have a go, you'd probably do the same for their discs. You'd check them out and see what they had. That's why most of us don't JUST throw Innova or Discraft. Personally, I have 4 brands in my bag because I like to try out different discs. Now the Nike ones are going to have a bigger price tag than the Wally World ones just because they have a swoosh on them.
But I like what somebody said earlier on in the thread, they can bring their big guns and maybe even make some quality products because of their big budgets, but at the end of the day, the people who have dedicated themselves to making our Z, CE, Opto, Champ plastics are going to run the game. Yeah, Nike has expensive ball golf clubs, but who are still the main companies? Callaway, Ping, TaylorMade. Just because Nike, Reebok, UnderArmour or whoever jumps in doesn't mean that it destroys the sport.
And as has been said, we're not big enough for them yet anyway, so keep playing the game, be the faithful followers of the sport and in 50 years if the "Big Dogs" come in, throw your beat in discs, buy from the "good ol' boys" and keep living the DG dream!