14 Karten in 9 Rechnern 

The question:

How can we have free transactions, but not make it possible for someone to cheaply DOS the system into oblivion by simply typing "while true; do bitcoind sendtoaddress `bitcoind getnewaddress` 0.00000001 ; done" ?

To solve this we ask:  What characterizes that kind of activity which is distinct from normal usage?    We can't tell that the DOS transactions are all coming from a single party because they can just use many addresses.  We can't really single out smallish transactions because regular users make small transactions and the attack would work just as well even it was moving 50 BTC in each transaction. What characterizes them is that they're rapidly moving the same coins over and over again.

Bitcoin days destroyed is a simple metric that measures coin velocity, and it's basically what the prioritiy system uses.  Sum(input_values * input_ages) / tx_data_size = priority.

Our priority system in effect uses the transaction's Bitcoin days destroyed to pay for them— evidence that the user isn't engaging in a maximum speed coin recycling— in lieu of fees.  The metric is directly connected to real DOS attack behavior, it doesn't depend on the impossible task of distinguishing users, it doesn't disproportionally penalize low value transactions, it expends a real scarce resource (though not one that users consider otherwise valuable), it doesn't actively encourage bad behavior, and it's demonstratively effective. If you don't have enough priority or pay a fee peer nodes will not relay your transaction, miners will not mine it— not until it does have enough priority via aging.

With this metric an attacker is required to have an enormous and near unending supply of unmoved coin in order to sustain an attack or they must spend on fees (or con some suckers into paying fees for them).

The downsides are that it can be a bit inexplicable for the users— "you can't make a free txn now, but you can after the next block??", which is made worse by the fact that the reference software doesn't really try to construct transactions in a way that avoids fees— and more complicated to find _optimal_ coin selections with this metric (it makes the objective non-linear). But otherwise it's a pretty excellent metric.

englischsprachiges "Subforum" ist gut 

There's http://bitcoincaptcha.org/index.php, not very great payout but seems to be what you are talking about

As always, do not forget to consult this page before evangelizing about Bitcoin: https://en.bitcoin.it/wiki/Public_relations

Don't send emails that make you sound entitled; those will just drop into the circular file.

If you want to be taken seriously, don't lie about "zero fees."  Any merchant accepting btc nowadays (and wanting to end up with usd/eur/whatev) will face significant fees. Once the market has gotten bigger, they will be able to spend btc directly, then we would be talking (presumably low) transaction fees only.

"No chargebacks" is a great argument, though.

You know what...

Think of it as your vote for Bitcoin.

Contact seller and ask if they accept Bitcoin, just that simple. Now, clearly politeness goes first, if they just say 'no' don't press mentioning it again. But most self-motivated sellers would ask what it is. And that is where you can briefly explain it to them as you understand it. If they would want to know details that are too long to explain say 'just google bitcoin' to them.

And self-motivated sellers is what Bitcoin need.

Korea has decided to ban trade for commercial game items from the second half of this year as a measure aimed at encouraging students to not waste time.