Yeah, but I think that largely depends on the degree of security you want to have in your blockchain. For example you could use something of a multi-party signing-scheme for consensus that regularly stamps hashes of it's own table into the bitcoin blockchain - this kind of scheme would be significantly less expensive to implement since you could pack thousands of transactions into a single bitcoin transaction. I'm not really sure micro-payments are the answer to add blocking to begin with though -
> You can have multiple inputs / outputs per bitcoin transaction, so presumably that's what he's talking about.
Actually that's not it. What I'm saying is that you can have any normal multi-party signature scheme, where every N signing-rounds you ensure some measure of canonical ordering by publishing the hash in the bitcoin blockchain. I think sidechains are probably formulated in a similar fashion but it's been a while since I've looked at exactly what they are doing, the trickier parts if I remember correctly are transfers of value on and off the original chain.
