1. No independent third-party audit of the source code (Satoshi could be one rich man one day).
2. No independent third-party audit of the latest development release of the client (nobody in their right mind would put money into a digital entity without security checks and encryption).
3. No trusted third party exchanges able to produce a contract guaranteeing the security of held deposits (my dollars are safe thanks to the FDIC, which is backed by the trust and will of 300 million Americans).
4. Evidence that 99% of the economic activity of bitcoin is generated by exchanges or miners (clear evidence of a super-bubble) - is there a real-world use for bitcoin?
5. Client is still early beta.
I asked these questions in a thread which is currently getting buried...
1.Bitcoin client is being audited by independent 3rd party all the time because they are open source. If you want to do your own audit, you may.
2. The deposits held are in the record of every single one of the clients blockchain. Every user holding the same blockchain you have are essentially serves as witness to you holding w/e amount of bitcoins that you do. This blockchain always will be the same on all clients therefore you don't need trusted third party to do any accounting to guarantee your holdings. What could be better than having the entire "jury" agreeing to the same facts that your claim are true on your accounting books? Because that is literally what is happening when bitcoin transfers ownership from one to another and is recorded on the blockchain ledger so to speak. Encyption is on it's way to be in the client itself shortly, but the option is already available if you seek to perform this function yourself via truecrypt or similar software available for free.
3. You have a choice to not use any exchanges if you don't want to. You are not investing in an exchange, but in bitcoins. Due to bitcoin being still at in infancy, exchange services providers have yet to come up with a bulletproof solution as of yet it seems. Not worried as growing value of bitcoin will simply demand a better exchange and free market will surely respond and meet that need at the right time. For now, I just consider all hick-ups at exchanges as early growing pains.
4. If you could actually provide the evidence that 99% percent of all economic activity of bitcon is generated by exchanges or miners, I will acknowledge this as a valid question rather than a troll attempt. Just as a quick reply, bitcoin is still at it's infancy and there is still a valid need to exchanges currently. This obviously will change as the acceptance of the currency grows with time and more and more business accept bitcoins directly reducing the need to exchanges altogether.
5. This comes down to your own level of risk tolerance. One thing for certain is that the code is open and transparent. If you are like me and others that are accepting of the risks, then you can give yourself the option to participate early in a new currency that was just created. If you also have the technical knowledge, you can easily see that the core functionality of the currency and it's cypto are very secure. Of course you should take responsibility of your own security at all times regardless of involvement in btc or not. Somehow I have the feeling that even when the beta tag comes off the official client, that it will still continuously be updated and supported. I don't see how this is any different than how it will be for the rest of it's existence.