I am not sure what this accomplishes, other than making the stats look better in their monitoring tool. They pretty much seem to admit this:

"Conclusion: the loading, parsing and executing of the async third party scripts are quite often very slow and this messes up our End User performance stats in New Relic."

Delaying the dynamic insertion of scripts until after the onload event, doesn't change anything. All the external crap will still be loaded. It might even make the external assets load slower.

Another solution would be to choose a monitoring tool that distinguishes between DOMContentLoaded (or the equivalent in non-Gecko browsers) and the regular onload event.

https://developer.mozilla.org/en/Gecko-Specific_DOM_Events#D...