Well, I did say they were like "ephemeral" extensions.
If I can reuse the formula in many spreadsheets, it becomes more like an extension.
Once upon a time, I couldn't imagine something in the browser like the interface for Yahoo Pipes. But once Javascript becomes capable enough, some programmer thinks of it sometime later, and here it is! So how is that not extending the functionality of the browser? The fact that the code has to be reloaded for each site just isn't a big deal for the end user until download times become a pain in the butt.
Yes, it seems basic. All software "extends" the computer. That is what's so fundamentally great about software!
