usability: people use excel just fine and many are even able to setup an ebay auction. I don't think using blockchain.info wallet or android bitcoin wallets is very hard. I agree usability can and will be increased, but that's definitely not what can make bitcoin fail.
Usability can definitely make bitcoin fail, because it creates a high barrier of entry that the average person isnt going to bother with. Hell, it took me three months after I discovered bitcoin to actually buy some, just because of the hassle it took to get money on the exchanges... and this was before the mtgox hack...now you need to show passports and other ID and wait even longer for money to enter/leave your account (which is why i havent added anymore to the system beyond my initial deposit.
Add in the complexity of the system (which isnt that hard to figure out, but does take a good deal of research to use), the fact that most people are not very computer literate (beyond basics like email, miscrosoft office, etc), and a block chain that's bloated to a few gigs (and gets worse everyday) and takes
forever to download, and you end up with a giant hassle that most people wont bother with.
Can these problems be solved? Some of them, yes. Can they all be fixed before BTC becomes a distant memory? I doubt it
scammers will run bitcoin to the ground: If that was likely, it would already have happened. Look at all the shit that has gone down, yet the community is growing... and learning. It's a social problem. With a non-chargebackable currency, you have to do business slightly differently and the technologies do support this (wot and stuff) are currently being evolved.
The very nature of a psuedo-anonymous currency (because its not truly anonymous, and traffic analysis can reveal a LOT) makes it prone to scamming. I've seen people run off from this forum with a few hundred thousand dollars, and guess what? There isn't a single bit of recourse. If someone runs off with my cash, at least I can get police/legal help. The cops arent going to investigate someone taking your imaginary internet money.
In my opinion, it is naive to think that rampant scamming doesnt affect the userbase. When just about every article on btc is about a crash or a hack or a scam, people are going to be weary of using it (and even more so when they see the barrier to entry). Hell, I wont use any other exchange but MT gox because it seems like every other month a new one goes down (and takes its users money and runs) and I only half trust mygox not to steal my cash (another reason I wont put more money in the system).
You can keep a influx of new rubes going for a little while (particularly with raising BTC prices), but that wont last forever. People will get sick of jamming thier dicks into beehives and losing all their money (and have, I dont see half the users I remember when I joined the forum, the lack of old timers should be concerning).
Look at the volume, with the exception of the bottom of the original bubble, its never really reached the level it had at the peak of the bubble...in fact, it looks downright anemic compared to how it was...how many times can that happen before it drops to almost nothing (meaning no users trading)?
I call BS, you just want cheap coins again.
Thats cute, but I measure my profits in USD, not BTC. The price of BTC is meaningless to me, all I care about is whether or not the days movement beats the spread/fees and whether or not there is a clear trend. If the answer is no, I stay in dollars (in fact, I stay in USD most of the time, unless I see a clear opportunity to make a profit so Im not exposed if/when there is a crash)