Typo or not?

I only go on Marriage & Divorce (to see if I can help answer questions), that's why I am asking my question here. I have noticed lately that some people substitute "then" for "than" e.g. Angelface just now...."we have been more like room mates then a couple for the past years...". At first I thought it was just a typo, but I am seeing it more and more. What gives? Are these all typos or are people changing the language, or are they just a bit ignor... didn't pay attention at school? Thanks everyone.