The evidence begins to accumulate that some professors either don't realize that the online realm exists, or don't know that their students have roughly the same reach in it that they do. Begin with A. Rickey's tale of constitutional law woe, in which his professor re-uses an exam question that not only appeared on a drive accessible to the class, but also included a model answer. In this thread about rumors that some UT 1Ls cheated on their conlaw exam, a couple commenters take the opportunity to note similar professorial incompetence:

The exam in question, Graglia's Con Law I, was three essay questions. Two of which were exactly the same questions he asked on the Spring 03 exam. No need to steal the exam when the prof gives it away. The best part though, one of those two questions was based on a real case, which Graglia helpfully gave the cite to in the body of the hypo.

"IrishLaw" (same as this IrishLaw?) says,

My second year at N[otre ]D[ame], our Business Associations prof said she was giving a short answer exam with some MC. She gave out a few sample MC problems to prep with. Sweet. On the day of the exam, she hands out the test, which was all MC. Fair enough. The kicker is, (1) the sample questions she handed out were from a past Stanford exam which she found on the web; and (2) our exam consisted of those questions on the old Stanford exam she didn't use as examples, which were readily available on the web complete with answer key.
Of course, before the test, a bunch of people had Googled the sample questions, done the rest of the questions as prep, and breezed through the exam. The lovely administration at ND didn't even have the courtesy to make the test pass/fail.

Thankfully, the closest I've come to anything like this is the professor who borrowed from a blog in the prompt for a writing assignment that had little-to-no effect on our grades anywa.