Very frequently, ISPs and core traffic folks filter these nuisance ports at their routers, so it's not as widespread of a problem anymore (e.g., you're not very likely to be exploited via NetBIOS from some kid in Romania).

However, this does not mitigate or even lessen the need for a firewall, especially on a cable network. All of your neighbours, who are presumably behind the same router as you, have unfettered access to each other's nodes, as well as yours, and it only takes one motivated chap to ruin your day through an exploit or an insecure service.