We've heard that Mac App Store Apps are restricted from installing kernel extensions (kexts) that are frequently used to provide system level functions in these utilities. Apps, as well, must be self contained and avoid use of undocumented APIs.
So.. apps that I could let any friend install on my machine without worrying about what sneaks into my system.
Do you use any OS X system utility? Chances are they break Apple's rules, they are unbelievably restrictive.
Yes system level tools won't happen through the app store.
They said the app store apps woukd be licenced to all of your personal machines.
So anywhere I login, it'll let me install the same apps

I suspect they'll be in my personal application folder too, not in the main application folder.
If you read the Mac App Store rules, applications like Office 2011, Parallels 5, VMware Fusion 3 would all be rejected. I'm curious to see how this works.
This is a problem. Especially Office, or CS4. BIG apps will need to be installed through regular means.
Those that are laughing with the tin hat people have to keep in mind that this is Apple we're talking about. They already have 2 platforms with a closed App Store and no other way to install applications. I'm not saying it will happen, but knowing Apple they could certainly try.
They will start to push this. They might even make lighter versions of Lion (closer to iOS) that only run App Store apps - which might run faster on a MacBookAir.
Mostly
it'll be so convenient to use Mac App Store apps for anybody on multiple Macs, that they won't leave it.
Like the iPod touch and iPhone, you can easily just "transfer" your apps, videos, etc to iTunes, but let's say you wanted to do a hard drive refresh and re install Mac OS X....will you have to rebuy the apps you bought from the Mac App Store?
I'm convinced this is all about their new data centre.
All your data, music, applications etc will be synced online. Log into ANY Mac and get all your data, music, applications etc. Until now, you couldn't just copy your app from one Mac to another (though many work that way.. not the system utilities or the biggest apps though...).
Every app on the Mac App Store will be portable.
I look forward to swearing at my Mac when it's crashing badly - then just reinstalling Lion, logging in with my AppleID, and letting it reinstall all my apps and documents and music on a clean OSX. I just hope it'll take my music etc from my iPhone if it's there rather than downloading everything from MobileMe.