Welcome to the Q&A Forum

I understand that keywords and adgroups within a campaign can affect the performance of other keywords within that parent campaign. I was interested to understand whether campaigns in my account can affect one another. I have an adwords account with around 30 campaigns. Some are heavy hitters and others get minimal to 0 traffic. Will these low quality campaigns drive up the costs of my high end campaigns?

Is there any value to buying a domain for its PR or age? Or is it no better than a brand new unregistered domain name? On the flip side, is there any potential danger of buying domains with PR and age?