Difference between SPOF and Block?

[pmeenan]

I usually use block when I'm trying to evaluate the impact of a given component to performance. Like "how fast is it without the ads" or "without the a/b testing" to judge the performance impact. I use SPOF to see "what is the impact to performance if the ads provider is unavailable" or to test all of the 3rd-parties to make sure there are no hard dependencies.