Interestingly, the problem with modern operating systems isn't so much that people have so much useless software running, but rather their fundamental design. I went to a talk last month by the creator of a new OS called Minix (which is just a proof of concept) that runs drivers as user processes (as opposed to in the kernel) and has a very small (4000 line) kernel (windows and linux are many tens of thousands of lines). It's really forehead-smackingly obvious that this is the direction in which we need to move. His goal was to have a 'TV-like' computer (which is to say, OS) where you take it out of the box, put it on your desk, plug it in and it runs perfectly for 10 years without you needing to be a computer scientist or even really understand how a computer works. I thought it was very interesting... you can download a copy if you're interested. Just google minix 3.
Perhaps I wasn't clear earlier. When I said it was an interesting hypothetical, I meant that the premise was impossible (that the gif was a virus). Assuming that this premise were true, it might have been harmful, though most browsers can catch malicious programs that are embedded in websites and prevent them from executing.