Your argument is "maybe not", which isn't adding much. So can we agree that if the reward you would get is actually less than the electricity+bandwidth costs of you leaving your computer on all day, then you're better off keeping the 500GB free?

Just like in Bitcoin, my free CPU cycles are better kept free because if I try to mine Bitcoin I would have to leave my computer on 24/7 and it would cost me more than the BTC rewards I'd very rarely receive?

We've literally just swapped free CPU cycles for free disk space, and we both know PoW is centralized and it's not worth individuals with a laptop to mine, but somehow the free disk space won't suffer the same fate?

Prior to AirBnB property owners left their homes unoccupied while they continued to pay property tax and upkeep on them during those times. Similarly, there are people with computers powered on all day that have disk space unused while they continue to pay for the electricity costs. If you assume these are the people who are going to make up the majority of the FileCoin network, this is effectively "found money" for those folks. (Albeit probably not much money.) This might not be the way it plays out, but if it does, your arguments about margins and electricity bills are moot: these costs are not increasing after the network is connected.

edit: Also even if FileCoin doesn't throw off a ton of ETH, presumably there will eventually be a wide array of services like the FileCoin network that you can transparently trade your liquid crypto assets into. For example, consider a person who happens to have 50TB of disk they don't need for the next month but would like to perform some low latency rendering jobs on the RenderCoin network during that time instead. They could easily just trade one for the other, increasing market efficiency for those resources. This example would be a small transaction in terms of ETH, but multiply that across the entire set of all computing resources, across all services, and it is a potentially tectonic shift in effective allocation of resources.

I leave my computer on all day anyways, I'm pretty lazy. Or rather, the cost of having to wait for it to boot is greater than the electricity. The fact of the matter is that I'm paying a large premium for a small slice of usable time and I'm not in the minority.