if you are not "premium" you can't play minecraft anyway. unless you pirate it. this question is pretty much pointless.
Oh aren't you cute?
I'd say a good 5% of users are premiums. The only thing that Premium really does that's useful is block ads and even then you can just install an adblocker for every window. I don't really care about the title or the premium forum. What would the premium forum even be used for anyways? It's not like it's pertained to any specific discussion.
Easy there :p. I think you're mixing up Curse Premium and Minecraft Premium. Curse Premium is where you don't see ads on the forums and you have that cool tag. Minecraft Premium shows that you've bought the actual game. The term Minecraft Premium has been used less since the dissapearance of Minecraft Classic, but the Mojang migrate page still refers to "Minecraft Premium" ;).
No I'm 99% sure I was referring to the Curse Premium. I mentioned the tag/title and the ads being blocked.
EDIT: Ooooooooooooh this is referring to Minecraft Premium? There's my blonde moment for the day, I should avoid all others now. Yeah I was mixing them up in my mind and not realizing what I was saying.
EDIT2: Oh my god it's even the title, I feel god awful stupid right now. Lol.
There are currently 3,344,853 registered members (as of when I started typing this) on this forum. Going by the numbers of people viewing threads, it appears that there are about 10 lurkers for every registered member. Presumably some of them are simply not logged in at the moment, so we'll call it 9, and round off the numbers to make that 3 million registered members and 27 million more unregistered members, for a total of 30 millon Minecraft players who read this forum. Now, some percentage of those people have stolen Minecraft instead of buying it like the rest of us. Let's say that's 10% of them (which is probably way high, but it makes the math easier). That would give us about 27 million owners of Minecraft (that is, "premium") on this forum.
I'm pulling those numbers out of thin air, of course, except for the one for total members and the percentage of members/lurkers. But it's probably as good a figure as you're going to be able to get, short of tens of millions of people posting in this thread!