I always thought a casual gamer was someone who owned a console/PC/etc and played on a semi-regular basis, as I do. It never occurred to me that playing farmville was actually classed as gaming in the traditional (not sure that's the right word, maybe mainstream?) sense of the word.
To answer the question, I don't think it's that much of a bad thing for gaming companies as it gives them a wider audience and more opportunity to make money, but it could result in less 'proper' games being produced in favour of an easy hit, thus alienating the fanbase/audience that got them to where they are now.
I don't know, really, the definition of 'casual' here is a little too loose for me to debate properly.
To answer the question, I don't think it's that much of a bad thing for gaming companies as it gives them a wider audience and more opportunity to make money, but it could result in less 'proper' games being produced in favour of an easy hit, thus alienating the fanbase/audience that got them to where they are now.
I don't know, really, the definition of 'casual' here is a little too loose for me to debate properly.