2004-10-04 : Does not increase the mana cost of the spell. It just requires a separate expenditure in order for it to succeed.

2004-10-04 : When this spell resolves, you either pay X mana or let your lands become tapped. The lands that become tapped are not “tapped for mana”. If you choose to pay, you may pay the X mana using whatever mana abilities you want to use.

2010-03-01 : Only lands that actually have mana abilities will get tapped. This includes basic lands and lands with mana abilities printed on them, as well as lands which have been granted a mana ability by some effect.