The only real "weakness" is theft/loss of your wallet and keys. Bitcoin is like cash in that respect, but with unique new properties. It's easier to hide and mo

The only real "weakness" is theft/loss of your wallet and keys. Bitcoin is like cash in that respect, but with unique new properties. It's easier to hide and move, but it can be stolen remotely (unlike paper bills). This is a problem and we all are working on different ways to decrease risks. E.g. by having multi-party authorization, "cold storage" (e.g. keys printed on paper), 3rd party services ("banks"), hardware wallets. Not real issues: - "No authentication for IP transfers" - not an issue, no one uses it. If you need to authenticate payment address, either get it over HTTPS, or use upcoming (in 0.9) payment API (same principle as with HTTPS, but without HTTP) or any other way that reduces risks of spoofing payment address. - "Energy Consumption" - not an issue. Miners spend as much energy as profitable for them, just like anyone else on the planet. Visa datacenters also consume energy. Who decides how much energy spending is "too much" if everyone spends what they can afford? - "Illegal content in the block chain" - not an issue with Bitcoin, but an external arbitrary threat created by feds. Same applies to unencrypted WiFi connection or someone sending a well-hidden picture in email attachment to you. Also: users are not required to store the blockchain. If you don't like a threat of "illegal content", use lightweight client to keep your keys only. - "Breaking the cryptography" - does not uniquely apply to Bitcoin comparing to, say, PayPal or bank wires. If some algorithm becomes weak, Bitcoin can be upgraded just like your bank's SSL certificate can be. - "Double-spending with 51% attack" is getting less economically viable with every single day as more people mine, use or simply know about Bitcoin. Also, it does not affect all the users, but only those with whom attacker transacts. And if that happens once, people would start sending expensive transactions directly to miners they trust to mitigate the issue. - "Coin destruction" is not a problem for society. Everyone's money gets more valuable when you lose yours. Divisibility is enough for a long time to come and can be increased on many levels, inside and outside Bitcoin core protocol. Lost/stolen wallet issue is covered above already.