If you're working with new stuff at work, documenting edge cases is always interesting. For example my blog was the only resource on the web for a lot of Oracle point-in-time recovery techniques when they rolled out that technology. I was just implementing it for a customer and documenting DR scenarios and testing them. I wasn't even really doing it to blog, more like advanced note taking in case I needed it in the future, also the knowledge that an audience would be looking makes you take care, not make assumptions about pre-existing knowledge. In other words it improves your technical writing skills.