All link building is manipulative in nature. Google wants you to leave the internet alone when it comes to links. This is evident in their recent judgment on even guest posting. You just need to decide which side of the fence you are on.
My personal opinion is that you look at the long term value of any strategy. What that is based on for me is whether it is sustainable and will there ever be any negative repercussions. If there will be, I stay away from it because I don't want that weighing on my conscious if their website goes bust. You have to face the fact that as an SEO, you have a lot of power. Companies have to cope with demand. SEO is so powerful that the volume of clients you bring in will change how they do business. New processes to handle the new client load, new employees, increase in vendors or vendor supply, etc. If the website goes bust because of something you did, you have now created a huge headache that is going to affect many different lives. Not just the business owner but their employees and vendors as well.
Is this strategy viable long term. That's the question you ask.
When it comes to whether you should build links or not, for me it's a resounding yes. There are many long tail keywords that local results aren't going to show up for. Many times, long tail keywords make up more of the searches for my clients than high volume keywords do. Quantity over quality in this case.
You also need to look at your goals. The goal for our company is always a #1 listing. We may not get it but we're going to shoot for it. If I move you to #1 I have quintupled your ROI. There are tons of different eye map studies out there but they one I usually use is 42% and 8%. 42% of people click on the #1 listing, 8% click on the second. If I can move you from 8% to 42%, how does that affect your ROI?
Quintupled.
Links are important. You can get by without them but if you're practicing a holistic SEO strategy, in my opinion, they can't be ignored.