It's no secret that I'm very bullish on REITs and other commercial real estate stocks. I regularly write articles on my favorite REIT investment opportunities and some of you would probably describe me as a "REIT cheerleader." But I am still objective enough to recognize that it's not all sunshine and rainbows in the REIT world. On the contrary, many sub-sectors of the commercial real estate/CRE market are today facing significant challenges, and this could lead some REITs to underperform going forward. I won't even discuss the office sector because we all already know about its challenges.