There's an argument that polyamory isn't real love, for one can really love only one.
One way to view this argument would be that "love" is a finite element that, if divided among more than one, also becomes less in each relationship, that it simply can't reach the "fullness it deserves".
I do not agree with that notion, I can't view "love" as something finite, to the point that I call the argument a myth. I base this on experience that I share with others who've been both on mono and poly relationships, that the love I feel on a polyamorous relationship isn't much different in intensity from what I've felt in monoamorous relationships.
Of course, there will be some that will argue that in that case, I didn't really love in my monoamorous relationships either. If you're one of those, I'd like to ask along with fellow poly people, how you know that what you feel is love?