This amusing note from dive into mark:

A representative for the company that makes PowerSiphon contacted me to correct my article on how to block spambots. I claimed that PowerSiphon was the spider with the User-Agent EmailSiphon. It is not. I have updated the article to retract my previous statement, and I apologize to the company for the mixup. You can draw your own conclusions about whether a retail web spidering product with a checkbox labeled “Extract email addresses” is a spammer’s tool, but it was not the specific tool I was seeing in my access logs.

Well, my feeling is that I would prefer any User Agent named “EmailSiphon” not visit my site. It’s probably a knee-jerk reaction on my part, but it is my opinion and I’m entitled to it.