They ask you not to poll any particular entry faster than once every 30 minutes and ask you not to connect to the service more than once per second. Whoisi doesn’t have per-host limits in its polling at the moment nor does it have a deterministic polling interval. (It chooses a random poll interval from 1 minute to 60 minutes to spread the load out especially during the initial polling service startup.)

Sadly, this affects adding new del.icio.us accounts as well. So if you’ve tried to add one and it fails, they might be rejecting access for a bit. I’ve seen this reported by a couple of people.

I’ll be writing a bunch of new code to handle per-host and per-RSS throttling and will add support for del.icio.us at the same time. (I need it for a bunch of other reasons, too. If nothing else because I don’t want to die when twitter dies.)