Is the Trusted Third Party an advantage or disadvantage in regards to wallet security? I'm new to bitcoin and have been reading some intros and FAQs.  Most features of bitcoin seem better than our current currency systems.  However, the one thing that strikes me is the ability to have your wallet stolen.  Either through malware, keylogger, in person, etc.  I've reading some posts on here about securing your wallet.  But the fact remains that it could get stolen.  And if it gets stolen your bitcoin balance is gone.  There is no way to recover it.  If you compare that to credit cards, when your card (or card number) gets stolen, the thief may make payments using the card, but the trusted third party (bank or credit card company) will usually not hold you liable and refund the money.
Therefore, if bitcoin were to become the most widely used currency in the world, people could lose their life savings just by a single virus infection or devious hacker.  Having that bank or credit card company involved provides that extra level of shelter.
Does anyone think this will hold back bitcoin use from becoming widespread throughout the world?
Security is, of course, an issue and when using Bitcoin you should exercise caution. That being said, it is important to remember that the Bitcoin community is rapidly evolving, and new technologies, systems, and services are being developed.

As Bitcoin continues to evolve, companies and computer programs will come up with new solutions to challenges and problems. For example, as you point out wallet security is a major issue. 

Already, companies are coming up with more secure wallets, that are hacker proof, and larger exchanges and service providers are being established. For a major company like Mt. Gox there is no incentive to steal Bitcoins, they have a profitable business model and any blow back from theft would far outweigh the incentive to steal.

Over time, companies will probably grow in size so that they can provide third party security comparable to a bank or credit card company for Bitcoins. Of course, it's relevant to wonder if they can do so while maintaining confidentiality.

Security companies will also likely grow in size past that point that they would consider trying to launch any type of scam. Think about it, do you think Norton Anti-virus would ever try to launch a virus program? Most likely not. Currently, most Bitcoin security companies are pretty small, but over time a few brand names will likely emerge. 

So to get to the point: No I don't think that the security issues you present will hold back Bitcoin. The Bitcoin community is creative, dynamic, and able to respond to challenges. Companies and programmers will see these challenges as opportunities, and will respond appropriately. 

My guess, Bitcoin will eventually be able to provide a sort of third party security, much like a bank, to those who want the extra layer of security, most likely for increased fees. Those who do not want or need that extra layer of security won't be forced to accept it.

So, is the lack of a third party an advantage or disadvantage? Honestly, I think that depends on the situation. If you want to have a highly confidential way to store and transfer money, having a third party involved means someone will be looking into your transactions, at least to some extent. If your biggest concern is having a secure way to store money, than third parties can provide extra security. That being said, there are ways to secure your Bitcoins, and as I stated I believe Bitcoin will eventually be able to provide similar levels of protection.

On a separate note since you are new to Bitcoin, if you are using Bitcoin, I would personally advise that you not keep all of your funds in one account. Divide your bitcoins into several accounts, and if possible keep the bulk of your funds secured offline. If you have a large amount of funds, you could even consider something like a safety deposit box at a bank.

Also, I advise going with trusted brand names, like Mt. Gox, or using service providers backed by Silicon Valley funding, things like that. These sites and services should be more secure.