'Homogenous' is a synonym for 'homogeneous'.

See: http://www.answers.com/homogenous and http://dictionary.reference.com/browse/homogenous

Not according to OED (see http://dictionary.oed.com/cgi/entry/50107551?single=1&qu...):

Article for homogenous only has two meanings listed: 1. Biol. = HOMOGENETIC 1. 2. Surg. Of transplanted tisssue: = HOMOPLASTIC a. 2.

I suppose the confusion in everyday speech made it into American dictionaries, but I still find its appearance in a magazine perceived to cater to intellectual snobs amusing.

While the OED may be considered the definitive source for the vast majority of words, many entries reflect the last print publication in 1989, and are not as in-step with modern usages. Language is continually evolving, and as always, it is best to consult a variety of sources.

I prefer "changing" to "evolving" to describe this phenomenon. It is certainly interesting to observe two unrelated words with similar spelling become synonyms in less than 20 years.

Definitions that are (1) in common use; and (2) not hidden behind a paywall are going to win out. The OED could learn a few things from the Economist.