Thanks to those of you who give Facebook the benefit of doubt. I don't work on this particular system, so I'm not qualified to discuss any specifics, nor do I speak for the company. I can say this though: People @ Facebook do care about these types of problems and work to solve them. I'm not some new grad; I've worked with large systems for a while. The scale is hard for me to comprehend. The systems I do work with illustrate very well that nothing is as simple as you think it might be and most of the obvious solutions get tossed out the window because they won't scale.