I will try again looking at it from their perspective because I am not sure I explained very well. What I am confused about is I am sending from a Bitcoin account that is not tied at all to the Waves account.
If I am running an ICO and 3 people tell me they will send 5 BTC and then give me a Waves address to send their tokens.
What happens if I only receive 2 payments of 5 BTC, how do I know "who" made the payment? (or who is the one who "did not" make the payment?)
It's exciting

but very confusing

Thanks in advance for any help.