It really bugs me how Facebook's MO seems to be to make every new feature opt-out, and often awkward to do so, in order to gain traction.
For example I can't even find a way to prevent people adding me to groups, other than outright de-friending them. That's a little nuclear for over-enthusiastic family members.
I suppose they'll add one later, after they are able to announce how millions of users are using the new groups feature.
One other interesting side effect of FB's aggressive stance on these features that I haven't seen discussed elsewhere is that it makes it progressively harder to be an inactive member.
I know many people who have created profiles which they feel obliged to keep (to maintain communication with certain family members, friends or colleagues) but are otherwise not terribly interested in it. FB is subtly adding a form of reputational decay to your profile. If you want your profile to represent you in a non-embarrassing way the next time a friend or colleague looks you up, you now need to log in much more regularly to un-tag yourself from photos and remove yourself from inappropriate groups (on top of figuring out whatever the latest changes are to your privacy settings...) Fun!
Others have noted another effect, that FB for them is becoming less interesting. All their (brighter) friends are "clamming up", and the remaining status messages and content from friends is becoming more infrequent and/or much less personal or simply interesting.
If I add in the effect you describe, it seems another disincentive to remain on FB. No good content, and you're constantly whipped to survey a changing privacy landscape for leaks and vulnerabilities.
But there also is not a way to control who tags you in photos. What's the difference? Both use social pressure to dissuade people from doing it when it is not appropriate.
1) Tagging a photo of someone generally does not imply their membership/support/interest in something (e.g NAMBLA).
2) It's very clear whether someone is truly in a photo, or it's a result of mischief. It's impossible to tell this with membership of a group.
3) Being tagged in a photo does not create a subscription.
I actually think there SHOULD be a way to prevent being photo tagged if you so wish, or at least prevent it becoming a hard-link to your profile/photos. My sister hates when people tag her in photos and will diligently remove the tags. I think that's a bit weird, but it should be her choice whether she can be tagged or not.
As for groups, I still fail to see the problem. You're notified when somebody (one of your Friends) adds you to a group; if you don't want to be part of the group, you remove yourself (and won't be able to be added again).
So, if your Friends aren't being malicious, there's no problem. If your Friends are being malicious, there's a very easy remedy (and you ought to reconsider who your Friends are.)
This is yet another one of those things that greatly reduces the SN ratio of Facebook.
Remember when apps were able to post to your stream willy-nilly? Facebook's stream became almost useless - for every one status update from one of your friends, there would be 6 more from apps like Farmville (seriously, Zynga's credibility for me went out the window when they started massively spamming everyone's streams).
Facebook had to backpedal quickly on that one and institute some pretty hard caps on what contexts allow apps to insert something into the stream, and the volume thereof also.
The more "curating" I have to do to make Facebook palatable to use, the less inclined I am to use it. For some people, photo tagging is one of those things (and IMHO ought to be fixed), and now they've introduced yet another thing you have to watch out for (on top of being a hawk on your privacy settings, in case Facebook decides to mess with them without your knowledge, again).
To be fair, this isn't the world-ending thing that a lot of outlets are claiming it is. But IMHO it is a clear net negative for the usability and appeal of Facebook. It's also fixing something that ain't broke - your friends can already suggest groups to you (as well as friends, pages, etc). If you really are interested in said group, there's already a perfectly capable mechanism for your friends to tell you.
The only people saying it's a net negative are people that don't actually use FB that much. For those of us who like it and use it to communicate with friends and family daily, the new groups features are long awaited. Group chat built into FB is so convenient! And fun.
In the real world, in order for a friend to add me to a group, they have to initiate it through some action: call, write, speak directly to, etc. It requires some sort of action on my part. If I don't wish to join an evangelical Christian group, I do not have to.
On Facebook, I can be added to a group I object to without my approval or knowledge. Removing myself from the group requires the action. I frequently go 4 or 5 weeks without checking Facebook and it's entirely possible that one of my friends (whom are friends, but not close friends) could have added me to some aforementioned group.
Facebook seems to want to model real-world relationships, but they don't allow for the way real-world relationships form and act. They want to cut out the inconvenience of us having to approve everything and just have it done automatically for us, which just doesn't work for me.
For example I can't even find a way to prevent people adding me to groups, other than outright de-friending them. That's a little nuclear for over-enthusiastic family members.
I suppose they'll add one later, after they are able to announce how millions of users are using the new groups feature.