Third of all, most of this information is already accessible on the Armory or in-game in some form or another. If these "stalkers" really wanted to stalk you, they could do so through in-game means. This is just more of the lazy man's version of stalking. If they're using RSS feeds to track your activity, then they're not really true stalkers. They're more like gawkers, really.
And, finally, the nail in the coffin (if you ask me) -- it's a game. It's a list of achievements in a game that you play for fun. Who cares if some website tells the world that you just killed Thaddius on Heroic for the first time ever? Who cares if you just broke 250,000 damage or healing in a single battleground? It's a game, it's a set of arbitrary rules and awards, and it means very little about who you are and what you do. You play for fun and that's all that really matters.
There are only two reasons you'd want to hide this information. The first is to hide it from opponents, so you could appear weaker or unknown to them and perhaps gain an in-game advantage. The second is to hide it from people who may judge you based on the amount of time you play the game. If it's the latter, then it's easy to re-roll or get a name change or perhaps even lower your play time. You are the someone who has something to hide, and it is you who is worried about being found out, for whatever reason it may be.
But... and here comes the very important but...
Throughout all of this ranting and raving, however, I never said that these people didn't have a legitimate argument. I simply disagree with how they are trying to fight it.
I, as a player and a writer and a developer, don't think that an option such as this should be a mandatory thing. Giving the player the option is always the best option of them all, and I see no reason to not add an "opt-out" option. If people want to hide this information, that is indeed their business, and not mine, or yours, or anyone else's decision. Even if we think their reason for opting-out is frivolous, we must respect it because it is their decision and their choice. None of my arguments above give a good reason why we should leave this option out -- they only say why the option may not be useful for all of us.
Even if they opt-out and this information isn't being broadcast, it doesn't impact the rest of the community in the slightest. As I said above, "Who the heck cares about an achievement, or a boss being downed, or what type of fish you're trying to mine?" It's a game, and everyone will do these things at one time or another. It's not essential information that impacts how a player plays, and it has no bearing on the game other than being cosmetic. If the people don't want to broadcast it, then that's their decision. If they do want to publicly broadcast this information in order to lord it over the rest of the community, well then, that's also their decision.
So, in short, give the power to the players. Let them decide if this new feature is for them. It doesn't hurt us if they say no.
Seraphina Brennan is the weekly writer of Anti-Aliased who may not agree with your arguments, but will back up your point anyway! When she's not writing here for Massively, she's rambling on her personal blog, The Experience Curve. If you want to message her, send her an e-mail at seraphina AT massively DOT com. You can also follow her on Twitter through Massively, or through her personal feed, @sera_brennan.