What about piggybacking off a torrent tracker? When people are downloading via bittorrent their IP addresses are kept by the tracker and are available for all nodes that connect. Maybe there could be a tiny file, announced on the multiple public trackers. While people “seed” it, their addresses are known and available as initial peer addresses. There are many public trackers available currently, with little chance all of them will be shut down at once.
Re: On IRC bootstrapping
Figures: Vasili Sviridov