You can find out when a feed is read but not when viewed.
Yahoo comes and gets one of my feeds say once a day. In the User-Agent string in my logs it does tell me the number of subscribers to that feed - but I don't know if/when/how often they actually look at that feed.
The other web aggregators don't even give me the number of subscribers.
Could you explain me one thing. Let's say there's an online feed reader (service) that checks for updates once a day. There are 10 people who've subscribed to my feed via that service. So that means my feed will be accessed 24 times per day. And it'll show me one source (IP address of the service) not 10 subscribers right? I mean not 240 times from 10 subscribers, but 24 times, like from one subscriber.
So if my feed has 1000 readers, I'll see only access from one source, is that right?