If it helps - there have been people (me, e.g. but obviously also others, but I don't have their nick or posts atm) bringing up the same arguments (about lack of backing, ponzi nature, bubble look, no economy exists etc) BEFORE the 30$ => 10$ "pop".
The "no backing" argument doesn't really fly with me, because it's voluntary participation. You should understand all the things you mentioned about Bitcoin before you part with any hard earned cash (haha) for some - if you didn't go in with your eyes open, you're just another chump. About the "ponzi" thing, I don't think it's the same thing - to my knowledge no one authoritative is claiming any type of guaranteed return in the way ponzi marketers do. Everyone I see promoting it in a big way is saying the same thing: this is a huge risk, with the potential of a huge reward. Disregard Rick Falkvinge being authoritative on Bitcoin.
About the "no economy" - well of course there's a scarce economy (it's not accurate to say there's
no economy, it's just paled by the rampant speculation). It's a currency without inherent worth, with no authority telling you you must accept it. Businesses are
rightfully nervous about entering into it, particularly with the demonstrated ability to swing wildly in value in a matter of hours.
It's a bit of a catch-22 that most of the speculation revolves around it having a useful economy, and that useful economy is being strangled by the speculation. Many of the heavy investors seem to simply want to buy as many as they can to hoard, expecting that someone else will do the heavy lifting of bootstrapping an economy.
I still think the project has merit as a currency, but I'm not going to hold any long term. I will leave it to others to speculate, though I have been having a pretty good time being a wannabe day trader. I'll keep accepting it in manageable amounts, liquidating it as I get it (or trading it off as quickly as I can for something else of value) and only gambling with what I can afford to lose.