Great questions! There are different schools of thought on this but there are a couple things to remember when considering your link building strategy. One, a good link profile to Google will include both followed and nofollow links from many different sources. They won't all have the same anchor text and some should not have anchor text at all. Having a link profile that is too heavily weighted one direction doesn't apprear organic and therefore could negatively affect your authority with search engines. Two, of course you would prefer links from sites that are related to your area of expertise and even organically that should be the case, but having a few links on other sites does round out your link profile. Just be sure that they are not the types of sites that are frowned upon by search engines. :)
Thanks for reading and a great comment. I appreciate it!