Considering the growing market of smartphones and other portable internet devices I would prefer ingame solutions over addons or external sources.
On the other side might be interesting to have such button for some kind of internal archive. Like if you have a supporter or something, you can mark that post and categorize it in some page, where you can have "silly suggestions" or "funny logos" and so on... so if you open that, you can see marked them and commented by you to fast look about where that interesting thing was.