Chance Gracia came across an interesting feature/bug when writing up unit tests for his application with PHPUnit. He was throwing an exception from a mock object and based on his annotation the exception is caught no matter the type.
Anyone who has worked with PHPUnit has most likely worked with expected exceptions and mock objects. The nice thing about working with expected exceptions is that we have access to a handy @expectedException annotation. I've gotten into the habit of using this for exceptions my fixtures should throw but also for when I'm using a mock object to verify a method call.
Some sample code is included to show his problem - a mock object is created for the "foo" class and a test to see if an Exception type is thrown is included on it. The problem is that the exception thrown isn't of type Exception, but of type "foo_exception" and the @expectedException annotation tells it to look for the Exception type. Because of this unpredictable behavior, he suggests not using annotations for these sort of tests or it could lead to false positives.