Common quote from Robin Jones Gunn, you may or may not have heard about it, but is "You go alone, you go fast, you go with people, you go far".
I think those quote only applicable to business that required a team work, and Investment is not one of them. Tho it will still applicable in the stage of learning about investment, but for doing the investment, help from other people will not matter much, and sometimes it even cause negative effect and confuse us as an investor. Investors need to take all decision by himself and own it, so whatever happened to their portfolio they will not blame others or became dependent to other people's opinion.