Macbook Pro 17in battery "expanding"!

I bought my MacBook Pro in Dec 2007. In sept 2009 the trackpad started malfunctioning and I noticed it wasn't sitting flat on the desk. I truned it over to find that the battery was "expanding" both out of and into the machine! Apple said they wouldn't help as it was out of warranty so I had to buy a replacement from my local Auth Apple Service Centre. The original battery ended up 3x its original size!!

Now my replacement battery is starting to do the same and the Service Centre say they "can't" guarantee the conditions under which the battery has been used/charged. I could understand this if it has simply been a slow death after too many cycles but this thing is slowly blowing-up.......again!!

Surely any product or part (of any kind) should at least be fit-for-purpose. Anyone had similar problems?