However, the "there was no downtime" seems a bit disingenuous given my own experience signing up for the service yesterday. I received many "service unavailable" messages during signup, after clicking on the email verification link, and finally after signing up. Searching Twitter at the time for "Pinboard" showed that many other users were getting the same message (e.g. http://twitter.com/davekincaid/status/15520511979167744) ... there were many others, but unfortunately Twitter's 'older tweets' search doesn't seem to be working now.
I actually didn't care that the service was down for me even though I had just paid to sign up for it; I figured you guys were getting absolutely hammered by the unexpected news around Delicious. However, seeing your response here was surprising - either you didn't have monitoring tools set up to show you that indeed there was downtime or we have a drastically different definition of 'downtime'.