While I am no fan of the company, it seems a stretch to say that their acquisition of PowerReviews last year could constitute a stranglehold on competition. If anything, the market for social marketing technologies is only growing, and the supposed network effects are negligible at best. While this chart is only an incomplete analyst of the market, it is clear that the market is quite robust.
So what happened? This comes down to hubris, dumb PR and executives who cannot shut up. The lesson here is not to be so publicly vociferous about wiping out your competitors.