Given how well LinkedIn has been doing of late, the headline for this post may seem a bit out of place. Just a few days ago, LinkedIn yet again exceeded Wall Street's expectations, posting strong third quarter results and increasing revenue for the sixth straight quarter. While its profits are fairly low compared to revenue, they, too, are growing steadily, and the company predicted another strong quarter to finish the year. Nonetheless, while LinkedIn continues to assert its dominance in professional networking (and has started to become a strong, viable business in so doing), the company still faces plenty of competition that could upset its comfortable lead in the space.