Firefox Weave has become Firefox Sync, and will be part of Firefox 4 in a cloud-based future.
Firefox Sync is basically a server-based store which holds your bookmarks, passwords, preferences and history, providing a consistency of experience that will eventually extend even to the iPhone.
Sync is available now as an add-on for Firefox, though a Mozilla blog post explains how that's only part of the Firefox cloud experience, which will include Firefox Home for the iPhone user who wants to take his bookmarks with him, and a developer's API for those who want to expand on the functionality.
Security is paramount to the point of imposition: connect to the Firefox Synchronisation server and you'll have to provide a password (of an acceptable length) and a cryptographic phrase which is used to decrypt your details once they've been downloaded (only encrypted versions are stored in the cloud). That's all very commendable, but won't sit well with the IE crowd, which values simplicity over security.
The service works, though we couldn't get open tabs or passwords synchronised and had to prompt it a few times to get even bookmarks replicated between platforms. There's clearly still some work still to do.
With more devices getting a usable browsing experience there is definitely a need for synchronising bookmarks, at least. Opera's Link function has been providing that for a while now, but because it restricts itself to bookmarks and notes it doesn't have the security issues that Firefox Sync faces in storing online passwords and identities in the cloud.
In the brief period when a mobile phone could fulfil the role of a laptop it was the consistency of experience which made the idea compelling. But if one could walk away from the desk and continue the same browsing session on a phone then that would be almost as good, especially as applications migrate into the browser.
Firefox isn't very mobile just yet, though it's getting there. Opera is mobile but makes no pretence of synchronising open tabs, so it's not ideal just yet either, but at least we're moving in the right direction. ®