No, I2C is multimaster system, there is "arbitration" supported in hardware on ATMega. Since it is open drain bus there is no risk of bus contention damaging the devices. If a device wants to send 1 but bus is in 0 it means someone else pulled it LOW and the one who wanted to send 1 "lost arbitration" and should stop transmitting.
SPI is single master bus.
EDIT: clarification