I have always enjoyed knowing that someone, somewhere has enjoyed seeing one of my photos, for whatever reason. I like it even better, I think, when it is a complete stranger. Someone I don't know just "favorited" this photo of mine today, and then when I clicked on the profile name, it turns out their entire photostream on flickr is construction equipment.
The first time this happened to me was way back, pre-blogger, pre-flickr, when I was keeping a simple HTML "online journal" on bitstream.net, and had posted an entry and a photo talking about how different areas of the country have different fire hydrants painted different ways, or even different names (fire plugs, anyone?) and someone contacted me via email saying something about how they enjoyed the post and the photo and were a fire plug fan in general. Somewhere I have that email (and my whole website) archived away, which I would have done anyway, but things like that from random strangers make it mean more as a shared experience, the creation and the consumption, so much more interesting to post, to blog, to share photos and ideas and even to possibly start and continue conversations and relationships that are as real as people I've known forever.
I don't care why you blog, but I know why I do.
It feels great.