Walking around the city, I often find myself trying to imagine which areas of street and sidewalk are the most traveled and what parts of the city are most popular.  I had already seen some examples of maps that had done this kind of tracking,  but I enjoyed learning more about the process of creating and putting to use these kinds of maps to use in Sarah William's lecture.  Before the lecture, I thought of cell phone tracking as just a creepy way for the government and phone companies to keep track of our movements for surveillance and advertising.  While the lecture further confirmed this, it also showed me the positive side of using cellphone tracking to locate high-traffic areas for city planning.  

It was also interesting to hear about the innovative research methods that Sarah Williams used, such as the street sign posts and flickr photo sifting.  I'd seen projects like the text-in information posts before, but had never been aware of it's use in tracking areas where people had time for leisure.  Sarah William's presentation made me much more aware of the uses of cultural technology like texting and flickr, if not, perhaps, just a little bit more paranoid about it.