g1smd - 10:10 pm on Sep 15, 2010 (gmt 0)
If any one of these services crashing can cause my pages not to load it makes me consider if it is even worth using these social networking buttons anymore.
Make sure the external features are - as far as position in the code is concerned - placed after your navigation and content.
That way, failure of those features to load will not affect the visibility of the critical parts of your pages.
I often stick a lot of those features in their own iframe.