Warning: shameless self-promotion ahead: I've also written my own JVM interpreter in JavaScript, which supports a substantial amount (perhaps most?) of the standard JVM, including threading, synchronization, reflection, rudimentary I/O, and most of the standard library classes (e.g., HashMap and Random). There's a lot of hackery involved but it's totally doable.

Also, mine runs on Rhino, which is itself written in Java, so it's C (JVM) running Java (Rhino) running JavaScript (JSava, my interpreter) running Java (the user program). How's that for meta-execution?

What will I be able to throw at the Mac/Linux users who show up?

I've often wondered who actually uses Yahoo. People who don't know/care just use what's in the browser search bar (Google 9 times out of 10), and people who do care use Bing. Wait, no, they use Google too. Then there's my grandfather who still uses AOL, but I wouldn't want them to lose 5% of their marketshare by having him switch.

This seems harmless enough to me if Comcast provides an opt-out service (like they do for their DNS-redirection). Someone who's savvy enough to opt-out of this is probably not as likely to get malware-infected, and the rest of the population probably doesn't care very much about the service either way. As for the monitoring aspect, I doubt that Comcast is actually examining customers' traffic any more as a result of this -- they're probably just using their existing heaps of data to implement this.

That's the kind of thing an idiot would have on his luggage!

I use DropBox to keep (small) files synced across several machines -- I know some people object to keeping data 'in the cloud', but that's what backups are for. DropBox means no forgetting to svn update or commit and has never really gotten in my way. I keep things like my Firefox profile (bookmarks, addons, etc) in sync by symlinking relevant files in my Firefox profile folders to files in my DropBox. It's a bit of a pain to set up initially but only needs to be done once and then my browsing session is seamless from one machine to the next. I also use this method to sync stuff like my calendar, address book (no $99 per year to Apple for MobileMe, thanks), and SSH and bash config files (always symlinked so that I never need to actually move things).