Last week saw the roll-out of a new version of Google Docs and Spreadsheets. One of the biggest changes was the announcement of "Folders". People were apparently confused by the old tagging paradigm, so they've replaced tags with folders. Makes sense from a usability point of view, but it's not until you realize that you can place a document in multiple folders that it clicks that this is just tagging with a different user interface metaphor. They simply stuff all the files in a database, and retrieve them by query, with a folder view layered on top.
The Register reported this under the provocative headline Google flirts with online OS. Indeed, it's very reminiscent of Microsoft's designs for Cairo's Object File System (never shipped) and the Windows Vista WinFS (never shipped). The Register might not be that wrong. After all, Google is already shipping one OS-like component for Windows… Google Gears.