One of my brothers and I are opening a new website, Free Home Shop, to the public tomorrow. A few weeks ago, while looking for good places on my other sites to link to it from, I asked another brother if we could link from his title insurance website. His response surprised me--title insuance companies are banned by law (at least in Utah) from advertising for, or getting advertising from, companies that generate title business (eg. real estate, mortgage, and such businesses).
I can only imagine that the purpose of such laws is to protect customers from getting locked into a particular title company if they get their mortgage from a particular broker, etc. But as an internet guy myself, cross promotion between complimentary products is such a natural thing to me that the ban seems absurd.
So we settled for a link from one of my brother's other sites (he's a lawyer too).