While I agree with you that blindly using CDNs without properly considering the tradeoffs is naive (this is why PIE does not use a CDN by default), I also think that the "CDNs have no benefit, never use them" attitude is similarly naive. As I mentioned above, there are some real benefits to using CDNs, as well as some real downsides, and calling those who make that choice responsibly "ignorant" or "lazy" is unfair.
You bring up some good points, so let's discuss these:
- You say you disable scripts from other domains. I'm unfamiliar, is this an option in IE? How do you set it? Is there a way to detect in code when a user has that setting enabled, so that PIE can automatically fall back to local loading? I'll gladly implement that if possible.
- I sympathize with your concern about reliance on third-party servers. That becomes a real problem if the scripts are loaded synchronously, or if the site can't function without the scripts. With PIE, however, neither of these is an issue in my opinion -- if it's configured to load from an external domain it will do so asynchronously so the page is not blocked from rendering, and PIE only provides visual effects which shouldn't ever prevent site functionality anyway.
Also, let's not fall into the trap of assuming that "separate domain" equals "third-party server". It's quite possible (and I think somewhat common) to use several domains that resolve to the same physical server or cluster, to enable the technique known as "domain sharding" to get around concurrent connection limits imposed by browsers -- I've done this in the past and it can improve site performance significantly, especially in old IE where the connection limit is low.
All good discussion.
If anyone wants to take a whack at drafting some guidelines on the pros/cons of loading from external domains, I think that would be a valuable resource for PIE users and I'd gladly include it in our docs.