Guys, it has been proven again and again and again, that it is possible to harm your competitors(and yourself) with backlinks. There's a case study on it every week, on this forum and on others.
Yet dozens come back with the same statement: "Google would not let someone harm someone else's website. It would be too easy to abuse".
To be clear, backlinks CAN hurt your site. My personal example, I have accidentally done it to myself (site-wide backlink from PR7 site with 100k indexed pages on 5 month old site with 800 backlinks mostly PR5-PR2). Within 24 hours Google had penalized hundreds of keywords which I was tracking. No, after 4 weeks, it has not recovered.
Search for this on here for recent case studies:
[CASE STUDY] Sandboxing your competition
[Case Study] Removing Negative Competition from top 10
Please stop assuming that "google won't let this happen". It does happen. The links don't get ignored in all cases. In some cases, they hurt you.
I doubt it. If it did, the possibility to abuse this would simply be too big.