While i don't doubt it it also doesn't mean they'll never 'spy' on customers, if the infrastructure is there the only way to know it's not being used for nefarious purposes is to make regular checks, something I'm sure people and companies simply don't have the resources for.
Instead of having to constantly watch the watchers I'd prefer if we weren't being watched in the fist place then we can all focus on more important stuff than whether the watchers are behaving themselves (that not only applies to Microsoft but all organisations who monitor their community, I'm looking at you GCHQ).