Real estate investment trusts (REITs) are designed to pass income on to investors in a tax-advantaged manner. So it is understandable that dividend investors pay a lot of attention to REIT dividends and yields. But every REIT shouldn't be judged by its yield, and a perfect case in point is AGNC Investment (AGNC -0.62%), which has a huge 14.9% dividend yield. Here's why income investors need to tread carefully with AGNC Investment.AGNC's dividend isn't an income panaceaBefore getting into AGNC's business, it ...