I also can see how it can help you (ie look at the stats at certain schools like Davis, a pretty large percentage of the admitted students also attended that school as an undergrad, so it definitely didn't hurt them). But I also don't think that not knowing anyone is going to hurt you. I think it's a very very small part of the consideration process, certainly much smaller than experience, gpa, gre, etc etc. And as far as I'm concerned, it's not something that I can really change, so I'm not going to worry about it. Sort of like that whole minority thing. Schools actively consider how much diversity you would bring to their school, esp. when considering out of state students, but I'm very vanilla in most things, so that won't help me, but I don't consider it to be something that hinders me either (others may disagree with this, but there's little I can do about it anyway

).
And you can also look at it like this, the vet community is very small, this is true. So if you know someone, it might be an advantage at some schools, esp. if that someone is someone important in your field of interest.
On the other hand, the vet community is very small, and there are politics involved, as there are politics involved with any community. So it is just as possible that Murphy's Law is going to screw you over, and the ad comm in charge of your application could very well be a foe of your Very Important Evaluator rather than a friend. I've never heard of this happening, but I imagine it's quite possible (esp. considering the eh, colorful personalities of most of the people involved
😀).