Each NIC (wired, wireless, etc) on a computer has a different MAC address. Given that a computer can have more than one Ethernet card (or whatnot), and ignoring the fact that some devices can modify their "current MAC address", is there a limit (theoretical or practical) to how many different MAC addresses a single PC can have?
This depends somewhat on the hardware and network topography - I dont know of a theoretical limit (save for all possible maxs), but the practical limit could be as low as low hundreds due to arp table sizes in switches, routers and other devices, and possibly also the impact of responding to broadcasts.
The next question woild be how to get this many macs - it must be possible to simultaneously define them on a single nic - as this is what virtual machines do. Likewise you may be able to put a fair number of network cards (eg multiple quad port cards) and further amplify each of these with VLAN trinking to switch ports depending on how you want to define the question limits.
Practically though, id suggest somewhere arround 50 macs being a realistic (but nowhere near absolute) practical limit.