You can use bitcoin for any amount you want. And yet, except for the drug sellers on silkroad, almost no one does.

I, personally, see the biggest disadvantage of bitcoin (1) the price unstability - it jumps up and down like crazy, and (2) the still unclear legality - from the tax endpoint, and the like. And (3) - also its biggest strength - it's as safe as your PC is safe. When someone steals your Microsoft Word documents or your Excel tables, who cares. If someone steals your wallet.dat, you are screwed. Period.

It may seem like a moot point, but both Mt.Gox - the largest exchange of bitcoins - and Slush - second largest miner - has had its servers compromised. And those are the highest end-points. Now think of all the users - the lowest end-points, who have "password" as their PC password. You want THEM to have all their money on their wallet.dat files, on their disks?

Now, drug sellers on silkroad really don't care about the second point, but much of the regular businesses do. On the other hands, the regular users have their lowly secured PCs as the only gateway to their money.

I am not sure if Bitcoin will ever get off, given all these circumstances.