Too many pings?

I have been wondering about this for quite some time now, and I can´t seem to find the answer. Most bloggers are desperately to ping the most popular services such as Technorati, this way Technorati will now that the blog is updated and it will have links and summary of the recent updated post, and this will/might generate traffic to the blog.

Many bloggers will then ping Technorati (and other services) more than one time for the one new/updated post. I have done something in the past week or so that I probably shouldn´t. I have “always” been using pingoat, and I recently found out that FeedBurner can also ping for me, and I discovered that I hadn´t removed pings to pingomatic in WordPress. So, this way I actually ping Technorati and the other services three times when I have an updated or new post.

My question is this, will that hurt my listing or my ping at these services? Or do they just ignore more than one ping? Because sometimes it seems that I can´t find my post at Technorati at all, and I am wondering if that´s because they didn´t list it because I pinged too many times? It could be thought of as spam pinging, but I don´t know how this works. It probably is enough to ping once, and I am using Pingoat for that.