Dominik,
Yahoo and the Washington Post are likely using the newly released Open Graph timeline features of Facebook. We're planning to incorporate those later this year into JFBConnect so you can post to the user's timeline different events that they are doing/taking part of on your site. It's very complex to get setup and something we'll have a lot of work to do to simplify for our users.. but definitely on our radar.
We did add a case to our feature tracker for the idea you mention above of a customizable login message depending on the page the user is coming from. I'm not sure how difficult that would be, so not sure when we'd be able to get something like it into JFBC. We like the idea though, and will investigate further.
Thanks,
Alex
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