Upon reading gnomeaggedon and his discussion of the Seven Deadly Sins of WoW, I mentioned that I felt meter spamming was a top sin in my book.
You would never see the lowest damage raid member linking the meter in the raid. It is generally first or second in DPS that puts it out there. Not everyone is equal with their abilities in the game and no one wants to be embarrassed. Link the meter in PM if someone is asking for it. Hell, just give him/her the link to get the addon themselves. For me the meter is just a personal check of where I am and not a boasting tool. Don't use it to embarrass others but as a means to get your own game in check.
If it's a guildie you see that is struggling with DPS, private message with a suggestion of a rotation or a website with some helpful tips. Be tactful but helpful.
One of the most popular damage meters is Recount from Curse.com