The landline companies though do have a fair argument. The bill says number portability has to go both ways, but right now, it's technically impossible for someone to take a cell number and have it transferred to a local telco. As I read the article, this is mainly because if one switches the number to a landline, the billing area wouldn't be the same as it would be for the cell phone with that number, since cell phones generally have larger local calling areas than landlines . . .
Interesting post on slashdot that mentions this could be bad for 911 calls . . .