I have experienced the same problem. It happens randomly to random pages and not all of them are high profile pages. I would chalk it up to it being a bug.
I have a flaky* DSL connection of 2.6Mbps and I notice the AJAX calls to facebook crap out.
* During wind or rain, cuts out for a minute about 4 to 6 times per hour.
The problem I am referring to (not loading completely and sometimes loading completely but not showing all the entries of a page) doesn't happen all the time, but happens often enough to notice.