JenSense is reporting that Google has had a bit of a mix-up, and sent some checks out to wrong addresses or payees. Google somehow cross-pollinated information from AdWords account into AdSense accounts.
If this happened to me I would be very, very upset. It is a clear violation of the Terms and Conditions that says:
You shall be sent by Google within approximately thirty (30) days after the end of each calendar month that Ads are running on Your Site and/or Search Results Pages if Your earned balance is $100 or more.
For me, AdSense is not my primary source of income, but for those people who depend on AdSense income, this would be a very serious issue.
This is the first time I have heard of Google making such a big mistake. As Jennifer pointed out, with competition coming from YPN (and soon, Microsoft), this is not the time to be screwing up.
I hope Google does a mea culpa and sends out checks to everybody who was affected.