I love how Pinboard deals with this issue: site remains online (albeit with limited abilities), all data is secured and backed up, users are encouraged to use the export tool if they feel the need and there are status updates on Twitter.
One thing that does work is our export page, and if you're feeling nervous about your data I encourage you to use it. We have fresh backups (from one day ago) safely stored on S3, but in these matters you can't be too careful.
Keep it up Pinboard!