I'm thinking that maybe this issue can't be cleared up without the risk of turning EOS ERC-20 tokens into 'securities'. It seems that those with money to 'invest' must do so on the assumption that:

1. EOS is going to be a great platform.
2. It is indeed beyond the reach of the SEC and other regulatory bodies.
3. Because widespread distribution of tokens is essential (for network effect), and the most committed token holders will be those who purchased ERC-20, the token most likely to be used will derive from the ERC-20 token.
4. The final EOS tokens will be issued in proportion to the ERC-20 token holdings, because otherwise a top-heavy stake distribution (like Steem has) may reduce the likelihood of widespread adoption.

I'm looking forward to investing my time developing software for the EOS blockchain, instead of a large token purchase, as this avoids making some of these assumptions. However, I've almost just convinced myself to to buy some tokens too!