Maybe you could get it to work with two plugins:
First, install the auto-join-groups, but beware, I think it is still the old version (1.0) in https://wordpress.org/extend/plugins/auto-join-groups/ and not the new one (1.1) which you can find here: http://brentandmary.net/2009/10/24/bn-auto-join-group-plugin/ I have tested it with BP 1.2 and WPMU 2.9.1.1 and it works. (It also works on WPMU 2.8.4 with BP 1.1.2)
You need to create groups that match your profile fields, wheter it is interests or location. Only ‘selectbox’ and ‘textbox’ type profile fields are supported. The plugin work backwards so all existing users will be connected to their corresponding group. Neat.
Then, I imagine, you can try some of the plugins that will email group members about updates.
thank you. I think I would end up having to create tons of groups. 
Or how about this? A side bar next to a users profile that shows other users that share common interests. Is that possible?
thanks
Yeah, but it is worth it… 
I had to create 21 groups (one for each region). It took me a couple of hours. Now it is much easier for people to find each other. I also created a page with an image map and links to all regions. I can see that people have great use of it. Not everybody understand that they can click on profile fields to find others.
If you need a ton, maybe you should rethink your structure? Because then people also would have to fill in a ton of profile fields? That might scare them off.
Another argument for creating groups – each group have their own RSS, making it easy to follow.
Yes, I think a sidebar could work. Then you have to build your own theme. That´s over my head.
In index.php and/or profile page, you need to add a string to get a specific sidebar, and then you need to create that sidebar, and put some code in it to gather interests and show all others.
Maybe you can hire someone to do this for you.
I was thinking maybe there was a widget out there for this. Something that could show users with common interests. I’ve searched with no luck. Guess I’ll try to figure it out.
thanks for your help.
as far as I know, users are auto-joining a Group by default in BP when they are writing a comment onto a certain Group.
But joining certain Groups during the Sign-up-process is definitely a good idea to implement.
I am also very interested i this functionality. The ideal for me would be a sidebar widget with something like “suggested friends” or “people with similar interests” that lists a few links to people who’s profile info is similar. A weekly email notification of these people’s profiles would also be fantastic.
This has same great implications because it encourages users to interact with people they don’t know and they are (might be?) more likely to do so because of their self-described similarities.
Anyone find a solution? Also looking for widget/plugin to show members with similar interests and match up various profile fields. The group idea is interesting, but could be extensive, i.e we have a field for state that would be at least 50 groups, not to mention we hope to go international.
I’ll add this to my list “plugins to create”. Not sure when i’ll do it but it is a good idea for a plugin. Surprised it hasn’t been created already.
