I want to add that I realize the legal issues make any PUBLIC pre-sale/pre-mine choice dubious. If you do public ICO then the tokens must be registered as securities. If you do PRIVATE pre-sale and then PUBLIC royalties from mining as Zcash proposes, then the miners apparently have to register as Money Service Businesses under FinCEN regulations and the coming G20 plan to harmonize these regulations starting in 2017.
Appears the only options for legal distribution are PRIVATE ICOs (that can include any qualified investors as so defined by the SEC but you can’t advertise this to the public-at-large and has to be viral within the qualified investor social network).
Or via PUBIC proof-of-work mining.
IANAL yet I think Ethereum violated the securities law.
Some have also claimed that PUBLIC airdrops might be legal, when these are not marketed as investments but rather for-use tokens.