When I was a kid I thought I wanted to have lots of dogs when I grew up but the reality of it changed my mind. I've done a lot of rescue work and fostering dogs and have had as many as 8-10 at a time. Taking care of them became work, they didn't get nearly as much personal attention as they wanted, and I didn't form close bonds with more than a couple. I prefer to have deep, special relationships with fewer dogs rather than casual ones with many.
I think two dogs is the perfect number for me. I have a Lab and a Boxer now. When I am busy they can keep each other company, but two dogs are less likely to fight than three or more. When renting, it can be difficult to find landlords who will allow pets at all, much less indoor dogs, and many cities have limits on the number of dogs even if you own your house. We walk/run five miles nearly every day and it's hard to control more than two dogs, especially large ones, when we encounter situations such as loose dogs. I like to travel, and more than two dogs is a problem there as well, as far as room in the car, potty breaks and walks, finding motels that will accept them all, etc. I can foster a third dog temporarily now (and I do take in and find homes for strays whenever I see them), but if I had three dogs I don't know if I'd be willing to take on a fourth. Besides my own selfish reasons of not wanting to deal with that many, it would rob my current dogs of the level of attention they are accustomed to, which wouldn't be fair.