Thanks Niels for this one. A new law in Germany came into force, which requires that German-based website owners must submit their websites for collecting to the German National Library. From the FAQ:

Why does the German National Library collect online publications?
The Law regarding the German National Library (DNBG) came into force on 29.6.06. This supersedes the German Library Law from 1969. A major aspect of the new law is the expansion of the collection brief to cover Internet publications, so-called "net" or "online" publications. The newly revised law adds online publications with no physical carrier to the library's long-standing brief of collecting books and sound carriers. This modernizes the Library's ability to preserve the digital cultural heritage.

Which online publications does the German National Library collect?
The collection field of online publications covers all text, image and sound-based works made available in public networks. The submission obligation covers both Internet publications with corresponding printed versions and also web-specific media works. Examples of online publications include electronic magazines, eBooks, university dissertations, digitized content, music files and also websites and dynamic applications.

What is the technical procedure for submitting monograph publications to the German National Library?
The publication is submitted together with the metadata via a web form. The preferred file formats are PDF/A and other PDF versions. If you wish to send a different file format because the document was not published in PDF format, this too must currently be packed into an archive (ZIP) file.

>> DNB, Frequently Asked Questions (FAQ)