Really? So you're going to declare income on the 20 hard forks in 2017 (many were scams / questionable value... if any, also not listed on US exchanges), and on the 50 hard forks this year? Don't you think this is a bit insane??
There should be some sort of value threshold or something similar. If your holdings of the hard fork's resulting coin is worth less than some trivial amount, then it shouldn't be necessary. But if for some crazy reason the market decides that another joke like Bitcoin Cash is actually worth some significant amount, then it seems hard to argue that this should somehow be immune to tax.
Sure I agree that there be a way to differentiate, but the only reasonable approach is that the new fork coins should be unrealized gains until when (or if) you use them (aka trade/sell). It has a 0 cost basis until proven otherwise. Seems simple; meets the requirements; stops bad actors. Only negative is IRS may only get long-term cap gains if someone holds it for a long-time.