1. They allow anyone to have a "bank" account that CAN NOT be seized by the IRS.
2. If you are careful, the IRS can't even know how much money you have in your account, or that you even have an account at all!
In effect, they will make paying most taxes voluntary. (in fact, not necessarily in law)
Please don't advocate tax evasion. Simply state that you can achieve certain levels of financial privacy with Bitcoin.
3. They allow you to do business with whoever you want, anywhere in the world, with complete privacy.
By default, Bitcoin is
NOT private. But if you're very careful (maintain separate wallets, not send transactions from your IP, etc) you can achieve certain levels of privacy. Hopefully Bitcoin will become more private in the future. See this thread about tracking transactions:
https://bitcointalksearch.org/topic/--24784, and this post about forwarding transactions
https://bitcointalksearch.org/topic/m.6038655. If you set it up properly, no one can even track how much money you have earned, so potentially, you could report as much, or as little of it as you choose.
Again, please don't advocate tax evasion. Also, you have to go to a lot of work (patching the client, using nonstandard tools, running behind tor) to actually have some semblance of privacy.
1. There are no 3rd party fees.
There are no 3rd party/centralized fees, but there can be small fees imposed by the "official" bitcoin client depending on certain factors.
https://en.bitcoin.it/wiki/Transaction_feesPlay poker online for money despite the government's prohibition.
Buy other prohibited items online. (Silkroad etc)
Again, please don't advocate illegal activities.