The drawbacks are that "theft" becomes "hacking." However, this still happens now anyways, so it really doesn't change much. People can trade more anonymously with Bitcoins just like if it were cash. Almost no tracing the exchange to the original buyer or seller. Almost. The government always has its ways. Make a hacker betray his own kind to get out of a jail sentence. There are always ways.
Most things we used to see in Sci-Fi movies are now becoming a reality. Star Trek used to have tablets, now what are our mainstream computing devices? Tablets. We have seen many movies that use "Credits" to pay for things instead of real money. Is this becoming the reality? Time will only tell what people decide to adopt. The newer generations are more readily accepting new trends, not having the same fears as the older generations.
Other countries accept Bitcoins already. We even use similar things here in America. I love to just scan my Starbucks card to pay for my drink. I haven't seen cash or have even been to a bank in years besides to get coins for laundry or the occasional money order. Honestly, we are already using a very similar system anyways. My paycheck comes via direct deposit, I pay everything with a card, I buy things online, I really have no need for cash.
Will we be going to restaurants and paying with Bitcoins or some other type of money soon? Will homeless people be begging for Bitcoins on the corner with their digital devices? Only time will tell.