when owning two dogs its one thing, but something about going from 2 to three you now have a pack mentality and things change quite a bit.
Yep. The average pet owner can barely handle one dog, let alone 3. My friend has five. Two of them are fairly stable, well-adjusted, reasonably obedient dogs. The other three are insane. At least two of them are biters (the third biter, the GSD, died last year). When you get two or more dogs with low thresholds and insecurity issues, put them together in a household with three inconsistent people, you have total chaos; even the good dogs can get riled up in a pack situation. Every time a person walks by, or someone comes in the door (even the people that live there), the whole pack sounds off, with hackles raised and everything.
It's extremely annoying. I don't know how their neighbors tolerate it.
On the upside, they have very few fights. They squabble all the time, usually over food, but very rarely is there bloodshed. However, I once made the mistake of letting these people dog-sit my GSD. I thought they were going to be coming by my house to take care of my dog, but instead they decided to bring her over to their house, and play a game of fetch with two dogs at a time... I told them my dog was possessive over toys and would not play nice with other dogs if there were toys involved. They did it anyway, and of course a fight ensued. My dog and the other dog had a torn ear, which of course bleed like crazy. I don't let them watch my animals anymore.
That said, if you have knowledgable, firm and consistent leadership in the household, and the dogs are worked with and trained individually, a pack can be manageable. A lot also depends on the temperament of the dogs involved. If they're all nutso rescue dogs, it's a lot harder, but if they are all of calm, stable, and biddable temperament, it's much easier.
And one thing the average pet owner definitely should NOT do is breed their dog and keep all the puppies. I have a client who bred their Jack Russell bitch--why, I have no idea--and simply couldn't part with two of the pups. ALL of them are neurotic and they fight constantly. With the three JRTs and one Golden, their houshold is complete chaos and they know they made a huge mistake.