Lightning Doesn't Strike Twice

Over the past few months, I have received a bunch of calls and emails along the lines of, "I see that you invested in XYZ Corporation and we're a very similar but noncompetitive company and thought that since you know the space you might be interested in investing in us." 

From an investors point of view, there are two schools of thought on this.  One school says diversify the portfolio (don't make the same bet twice) while another says the only way to get alpha is to *not* diversify. 

In my experience, the vast majority of investors are in the "diversify" camp which means as an entrepreneur you shouldn't waste your time talking to investors who are already invested in your market.