This slideshow lost all credibility when it said to put your analytics in the <head> tags. Sure some analytics providers might recommend you do that, but that is wrong and only serves to
A) Slow your site down
B) Introduce a single point of failure into your webpage
All scripts should be loaded either async or at the end of the dom.
If you load the analytics script anywhere other than the head, you potentially miss user input while the page is loading. For a slow-loading page, this could make you lose out on useful data. I realize that this argument is somewhat circular.
You should avoid including script tags in the head because it introduces single points of failure in your app. Losing a few ms of 'analytics' time is better than providing your users with a broken site because your analytics scripts (or any other hosted JS files) didn't load and waited 5-15s to timeout (depends on browser).
A) Slow your site down B) Introduce a single point of failure into your webpage
All scripts should be loaded either async or at the end of the dom.