Hi Raymond
Very nice question to ask i also see people in my industry using the same technique to aquire tons of backlinks, but as you consider about penguin 4.0 as it is now using the core alogorithm as a real time, one or another it will get penalized by google i think its not a long term strategy to sustain in market
Note: the key points in seo as we are a marketers is not to rank #1 in google . we need to just build the trust, great UI/UX interactions on our website
