Not a lawyer, but I always thought maybe someone could take your code, modify it to produce variations A, B, C, the three major use cases of your code, and slap patents on those modified versions of your code. So then anyone who wants to use your code with any of those three use cases in mind (i.e., most people who would want to use your code) would then likely be in trouble.

Or something like that.

A second issue would be one the author of the article seems worried about, which is that without a warranty-free clause people might sue you for bugs in the code. If you're distributing your code, with a line like "free for everybody to use," there may or may not be implicit quality guarantees, according to the article.