TechwareLabs has published a editorial on Synthetic vs Real World Benchmarks. Here's a clip from the editorial:
Do you find yourself often confused by reviews you find online? Are the results that you see much higher than those of your system or do they make any sense at all? Read our explanation of Real World vs Synthetic Benchmarks and find out how to read those reviews. We explain what you should be looking for and some of the tricks used by other sites to affect their results.