I do have to disagree because I expressed needs to diversify. I am not saying that marketers should take 100% of their time and divide it equally among all channels, however, ignoring a channel is a no-no. Search is all emcompassing and so if marketing in real life. Whether you are trying to rasie your SERP slot or meet and greet at events with potential clients, nothing should be ignored.
I agree that focus should remain on the most successful channels, but diversification is key. For example people largely ignored google+ at first because it didn't have a huge member base and popularity. However, now data is coming out suggesting that Google+ can have a large impact on search is vastly rewarding those marketers who at least spent some time setting up a Google+ page and getting a good foundation of follows and +1's over the past year.