I'm not a nutritionist, but my sense is that it would take A LOT of whey protein to really over do it... I'm talking body builder trying to really really bulk up and taking lots of supplements that are all based on whey protein.... over do it.
Personally, I prefer Soy protein... because me sense is that it's more natural. What I mean by that is just that I believe from an evolutionary perspective that as adult humans we're more designed to consume plant matter then dairy. Dairy's great when you're a kid and it came from your mother... but it's hard on your adult body to digest. Plus, since I have a cheese addiction, I figure I will get my share of dairy from that source.
Finally, I'll add this other recommendation that another fitness minded friend of mine offered. He suggested that I make a point of mixing up my protein sources. Include some dairy, some soy/beans/legumes, some meat, some fish. The point being that all of these proteins have slightly different amino acid components and variety always helps your body get exactly what it needs.