Is that so? I don't think so. Malayalees are spread out all over India and all over the world, in fact. I live in the Middle east. Here, every Arab knows 'Kiraala' (Kerala). Trust me, they do. One of my colleagues once asked me, "So many beoble from yoor Kirala...Kirala anozer kanthry maybe? More beeg zan India?" I had a good giggle before I explained briefly the demographics of one of the smallest states of India. She wouldn't believe me until I showed her a map :P Besides that, some of them have heard of 'Bumbay' (Mumbai) and 'Bingalur' (Bangalore). End of story.
See the figures from Wikipedia...
There is an equally impressive number of Malayalees who work outside Kerala in other states. Owing to the high levels of education, the state is not able to provide enough suitable jobs for the tens of thousands of job seekers that graduate every year, thus forcing them to move to other states in search of jobs. We even have an apex umbrella organization for all Malayalee Associations of Malayalees who live and work outside Kerala - Federation of All India Marunadan Malayalee Associations :D
Watch this!
Nope, we're not obscure alright.
Edit:
So apparently a lot of people have chosen to completely ignore the write-up and concentrate on the fact that I had posted actress Vidya Balan's photograph. After a lot of arguments regarding her ethnicity (which is in no way relevant to the answer) and after my repeated attempts at trying to make people understand the reason why I posted that image, I feel the need to add a disclaimer...just to stop the tirade.
I don't know Vidya Balan personally. We are not related for me to throw strong claims on her family and background. Whatever I said was based on what I have read in film magazines, on the internet and on what she has stated in her interviews. If the truth is the exact opposite of all that as everyone else is claiming, then I have nothing to say.