I'm sure that on an occasional late night, I have been guilty of one or more of those errors mentioned in that article. Lately I've notice more of a problem with then/than being used the wrong way, even in writing which one would not expect to find them used in that way. It seems to be a fairly regular problem in blog posts.
Than = comparison (more than or less than)
Then = temporal, sequential, or consequential (used in an "if this, then that" statement)