It's against the rules in DnD, sure.
But does it really make that big of a difference? If you play a Wizard, and I play a Sorcerer... I don't feel like you're overpowered. You're spending a lot of money on scrolls, most of which you'll never get around to memorizing because your active list is limited and tends to be filled up with favorites.
Meanwhile, I'm over here twinning and quickening spells and basically wrecking house.
Shrug. I guess it just doesn't bother me that Wizards can learn Cleric spells. In fact, I kind of think the Wizard needs it to compete with other classes.
