Yes, because every kid (at least in the 'developed' world) nowadays has web access but not every kid can install software on the machines they are allowed to use (for instance in school, the library or their parents' machine).
And, they can very easily show it to there friends, if it is in javascript. My niece loves designing webpages that she shares with her mates. Of course, getting her to program rather than put up pictures of twilight is another issue.
Scratch is definitely a cool introduction to the world of programming. But I worry that in its attempt to make programming accessible sets up kids for a rude awakening. Most "real" programming isn't like that at all. Yet the kind of code I wrote in the 80s in Apple BASIC isn't so different "in kind" from a lot of the code I write professionally today.
Sorry for posting so many comments: I'm a teacher so the issue of computers, programming, and education fascinates me to no end :)
Typing. The physicality of an interaction is not to be understated. I've seen wizards with specialized interfaces (Flash, PhotoShop, Final Cut, etc) struggle miserably with text based input.
Yes, but programming is about patterns, and, in my opinion, patterns are more simple to spot visually than with text.
It's maybe more important for a kid to learn that than learning about the "materiality" of programming.
Any particular reason it needs to be web-based?