Gnaffel: No. What he are talking about, is that you need to allow bitcoin clients to access the internet, eg you need to open port 6667 to irc.lfnet.org and port 8333 to * in your payment gateway, hotspot, firewall, whatsoever thing you are using to prevent users who have not paid from accessing the internet.

Also beware of tunneling users, in other words, users who SSH's or SSL's over 8333 to bypass payment and surf for free. A wise option in this way can then be to have a empty bitcoind running (with no coins inside), which your firewall NATs all :8333 traffic to. This bitcoind will then be like a "proxy" to the world. The user does not need to send the coins to that bitcoind, thats bitcoind only connects the wifi bitcoin network to the wide bitcoin network. and passes transactions further and back. Then you don't need to have 6667 open. (Or you could set up a fake IRC server which all IRC traffic is NATed to, which only have one channel #bitcoin, which reports your gateway, eg 192.168.0.1 as a bitcoin node).

Dont allow rpcallow=*! Its enough that they get a connection to a bitcoin node.