In case you missed it, there was some bruhaha over a recent change in WordPress where pinging went from being instant to being sent once per hour. Karamell.net argued that this change halted the real time web and that it would negatively affect announcement services such as Google news. A counter patch was then made to reduce the wait limit to 30 minutes and also bundle pings together. Then after all the discussions were made, the final verdict was to restore the original behavior which means pinging takes place when the post is published as well as any time it’s been successfully updated. The changes will be in WordPress 2.8.3 if released or WordPress 2.9.
At one time, I removed the Ping-O-Matic code from my WordPress install because I believed in the rumor that if I published or updated content too much, I could be banned from these pinging services because of so many pings. While it looks like that might still be a possibility, I’ve since learned to schedule posts and try to keep editing down to a minimum.