I suppose this has been disscused before but, recently I was thinking that if within campaign groups homebrew may be shared, and as far as I know one may create private homebrew, how will use of this as (tedious) piracy be prevented? What would stop me from copying material from the books to my personal "homebrew"?

Will all homebrew be monitored? Or will it need a subscription fee because of this? If so, I'd guess a subscription would have to include PHB and MM content, but then why would one buy access to those books then? Would subscription costs be lowered if one buys access to all content then?

I'm pretty sure doing that would be against the TOS for the use of the tools/site.  That being said, the only homebrew that will be regulated (as far as I know) will be the homebrew that is uploaded for public use.

I would guess that anything made public would probably have a report feature of some kind. I'm sure they'll have some staff monitoring it but without active participation of the community to report illegitimate content, that'd be a full-time job for a dozen people at least.

At a guess, policing the non-public stuff would be much, much harder. I'd wager it'd be hard enough that you could feasibly get away with it with little chance of ever getting discovered. Lot of work to manually create all that content yourself though and, ultimately, a pretty crappy thing to do to the people who made the site that you're using to host that content, not to mention the people who made D&D in the first place.