Archive.org already does that for you. I also had a similar idea of tracking a startup through history (showing everything from historical alexa traffic to goo

Archive.org already does that for you. I also had a similar idea of tracking a startup through history (showing everything from historical alexa traffic to google news to tweets to screenshots to blog-mentions). Screenshots alone won't give a lot of information but if you add meta-information to it, you will be able to see the startup's evolution.