googling around a little, it appears that mexico has been updating their immigration forms over the last couple years. it looks like maybe instead of three days, you get seven days before you need to have a tourist "visa".
also, they are going to come out with a tourist visa that is valid for 10 years for relatives of mexican citizens.
if i had to guess the change at the otay and san ysidro crossings is that there is a pilot program to allow/require visitors to obtain the visitor's permit at the point of entry from the border entry officers instead of having to go to the migration office and do it after entering the country. lol @ the shitty reporting by everyone who has reported on it.