If I have {Sphere of Safety} out (can't be attacked unless they pay x where x is the amount of enchantments you control) and on of their creatures has {Furor of the Bitten} does it still attack ignoring the sphere, only attack if they can pay or are they somehow forced to pay and penalized if they don't?
In these cases they may choose not to pay and therefore give up the actual ability to attack.
The opponent can choose not to attack. From the Sphere's ruling on Gatherer:
10/1/2012 If you control Sphere of Safety, your opponents can choose not to attack with a creature with an ability that says it attacks if able.
Thanks