well, they do a lot of pounding i will say; i hear it's a startup webspider so it's only understandable that they aren't as kind as google/yahoo...
I'd just monitor it, if it worries you, ban it in robots.txt, else i wouldn't worry about it...
Keep in mind that NO robot automatically reads your robots.txt as soon as you update it, they instead cache the file for up to 2 weeks, so even if you robots.txt it there won't be an immediate change.
