It's a neat idea, but I can't imagine using it. Do you really, really trust Google with your business? What happens when google decides to "fix" something in one of those frameworks that the upstream developers disagree with? Even worse, what happens when your app is irreconcilably broken because of something that happened at Google? Worse still, what happens when your app somehow becomes reliant on Google's version of the framework(s), and you don't realize it until it would be too expensive to unhook yourself from Google?
There's nothing new about depending on external parties - if your site hosts ads (or uses an external stats service) you're already running code hosted elsewhere, so you should probably be comfortable linking through to Google (I trust them a lot more than most ad networks). The question is always "do I trust this provider not to screw me over" - Google's developer network stuff HAS to be trustworthy or they'll lose the hearts and minds they've been cultivating overnight.
As for your app becoming reliant on Google's version of the framework, you can always download the JS file they've been serving and host it yourself. You can't get locked in that way.
As for your app becoming reliant on Google's version of the framework, you can always download the JS file they've been serving and host it yourself. You can't get locked in that way.
This misses the point. I'm not concerned about where the file comes from. If breakage occurs with regard to where the download comes from, a few customers get annoyed while you fix it (or even better, you implemented caching and customers never know the difference). That's a normal and expected maintenance issue that you plan for.
What I'm really talking about is the content of the file. If Google fixes bugs or adds features and you don't realize it until your app has become dependent on Google-specific changes, it's not an easy thing to fix. This is a different problem than getting screwed over by ad providers.
Aah I understand where you're coming from. I would be amazed if Google made changes to the libraries they are serving up (since it would undermine the entire concept of the hosting service).
It would definitely seem to go against the motto, right? You need look no further than Microsoft (and other software vendors whose entire strategy is based on lock-in), and assess the probabilities for yourself.
The scripts look like they're organized by versions, ie ajax.googleapis.com/ajax/libs/prototype/1.6.0.2/prototype.js, so google can't really do any 'fixes' if they want to stick to the original authors' versions. Being afraid of have to 'depend' on this isn't a big problem; it's just a text file. You can create a constant in your codes for the URL string so that you can change it easily. The Script.aculo.us and other libraries are pretty big, so having it load from Google would help a little.
Maybe one possible solution to my concerns would be to keep a table of sha1 sums of the version you want to depend on, and check them periodically (randomly select 1 of every 1000 visits to receive the checking code that reports back to your backend).
I just have an instinctive wariness of this kind of dependency, even if the cost of avoidance is a performance penalty.
