It is a special nokia battery that nokia made (well, not that particular one), it is just that there are more of them used, becasue there are more phones. And no, it isn't in every cell phone, it isn't even in every nokia. And no, I wouldn't buy a $7 battery (adding problems there?) from ebay for my phone - if it is worth buying a a decent phone, it is worth getting a genuine battery. Not all batteries are created equal, and yes, I know someone who had a non genuine battery that caught fire.