I personally have encountered poly relationships before, both first-hand and second-hand, and my biggest conclusion was that I was not willing to spend the time required in order to pursue more than 1 romantic relationship at a time. I am big on having time to myself, to do my own thing, to just be by myself and do whatever I feel like at the moment. When I date someone, I usually like to see them every 2-3 days, or roughly 2x a week minimum. To date 2 people, assuming I already know both of these people and don't have to spend time meeting people/getting to know people/going on dates, I'd find myself spending 4-6 nights a week on dates, or at least, hanging out with each of these 2 people. (Mathematically speaking, of course.) That only would leave me with 1-3 nights to hang out with my friends, not to mention spend some quality time with good ol' me! When was I going to get any reading done, for instance? Or writing or book-binding (just throwing out theoretical activities at this point)? Or even just vacuuming, dusting, feeding my cats and taking out their dirty litter?

That has always been my fundamental issue with the poly lifestyle; if I am interested in someone, I want to see them more than once a week. But I don't think that scales at all when you throw in even 1 more person into the situation. You either spend less time with each individual than you'd like, or have no time to yourself/your social life outside of dating.