_If_ this is technically feasible (I don't know) then not just Firefox, but also Seamonkey, Galeon, Opera, Konqueror,...? should be supported.

Wouldn't this imply that Epiphany can be a mini crack tool?
Let's say that I'm at my coworker's desktop and he leaves me there with a Epiphany window so I don't get bored and he's Firefox opened session isn't lost (like his gmail, I would have to log him out to log me in).
Then I use this option and steal his gmail password, next I procede to steal his girlfriend.

Well, if the passwords aren't protected by a master password and you have access to your friend's account, you could steal his gmail password (and presumably his gfriend) without the need of Epiphany as a "mini crack tool."

It would be nice if Epiphany could import password protected passwords too (given the password, of course), but importing unprotected passwords would be 95% of the problem solved.

As it stands now, users can copy key3.db and signons.txt from $HOME/.mozilla/firefox/profile to $HOME/.gnome2/epiphany/mozilla/epiphany and all their old Firefox passwords will work fine in Epiphany.
It should be fairly trivial to copy these files over a similar way bookmarks are copied, and it would make it easier for users, especially less technical users to switch to Epiphany from Firefox.

Opera and Konqueror would obviously be harder to do because Epiphany would have to do extra work to understand their formats, Firefox's format and Epiphany's format are the same and GNOME users are more likely to be running Firefox than Opera or Epiphany, so I'd reccomend adding an import Firefox passwords feature and not worrying about other browsers, the same way it's done for bookmarks only from Firefox (I think) currently.

*** Bug 171228 has been marked as a duplicate of this bug. ***

Er, more likely to be running Firefox than Opera or KONQUEROR, that is.

Is that to say that the import should be proposed the first time Epiphany is started? Or that it should be done each time Epiphany is started and detects that there was at least one modification in Firefox's passwords? Or even have an “Import passwords from […]” button e.g. in the “Personal data” dialog, under the “Passwords” tab or maybe even under a “Import settings” in case we want to handle several things?

It should only be proposed the first time (i.e. when the profile doesn't exist and we're not doing a --private-instance). Additionally, a File->Import... item might be offered to do it on demand.

Synching epiphany and firefox' bookmarks/cookies/etc is much harder to do, and out of scope for epiphany (could be an extension, but I don't think that's worth the work).

It's still doable to copy your firefox password data to the ephy profile and then run the profile migrator manually to suck in all the passwords. I think we should provide an option somewhere to import them after the fact though, it would be useful for people that want to switch to ephy but have been using Firefox for a long time.

Well we don't have accounts. Importing passwords from Firefox would be fine; patches welcome.