1. Why is it becoming harder to mine new Bitcoins? Is this an artificial constraint imposed by the eventual finite supply (i.e., it's controlled by the Bitcoin client software), or is it just a natural consequence of that?
2. If it's simply to do with the client, why couldn't one fork it with different parameters, but while still manipulating the same blockchain?
3. Is having an upper bound on Bitcoin, to be reached sometime in the next 25 years, a "good idea"? Will this be 2040's equivalent of "640KB should be enough for anyone"?
4. I would be interested to hear more about the "real life" problems that Bitcoin faces, particularly (as I understand it) the increasing verification time which makes it less-and-less attractive to use as currency.
5. What the spat between the developers was all about a few months ago? I don't remember the details, but it was about increasing/changing the parameters of the software, so may be related to my above question.
6. It mentions that the Ethereum blockchain supports "complex contracts and programs" and that this was its novel feature. I was under the impression that the Bitcoin blockchain also had some kind of contract/script support, but no one (at least when I read of this a few years ago) had done anything useful with it. Is this the case? Moreover, what sort of neat things could be done with such a feature?
7. Again I might be wrong about this, but I read that there were a small number of really big mining farms, with specialised hardware, that have somewhat disrupted or put an unnatural bias on supply. Is that such a problem, or do people not really care? Similarly, it would be interesting to hear about the "crashes", like the Dutch Tulip-esque crash in late-2013 and the whole Mt. Gox thing.
8. How are people utilising blockchain technology (i.e., distributed ledgers) to do other things, not necessarily to do with currency? Such things often appear on HN and generate a lot of hype, but the fact that I can't remember any examples suggests that they quickly fade into obscurity (i.e., it was the wrong buzzword for their problem!)
9. While it'll obviously vary between jurisdictions, it would be interesting to hear how various governments view Bitcoin with regards to things like legitimacy, taxation, etc.