You're likely to find many different viewpoints on this, it should be clear though that there are Doms out there that want exclusive relationships.

I'd have to agree with vox that I wouldn't always call it polyamorous because of what that word implies to me. I'd also have to disagree with IAmCanadian, a harem sounds good to me.

do You tell her right away?
Yes, IMO, it is very important to make these things clear up front and to be honest about whether I have other subbies - online or r/l. That includes whether or not I'm looking for a relationship period, much less something exclusive.

But that's just me, different people likely have different ways of broaching this subject. I'd rather have her know where I stand, even if it doesn't score points, than deal with drama down the road. If she doesn't like it, we can go our separate ways. If they feel they have to keep secrets, say all the "right things," or present a false front, it's a sign of insecurity or desperation. Again, just my opinion.