Unless you have an explicit need to hide x group's links from y group, you shouldn't have an issue. If you clearly state "here's the group link page. Use it" and they go there and they subscribe, it's all good. You don't need to control people (no! You can't follow my twitter account!) you just need to provide value (Here's my group link page, with all your shiny links).

It isn't that much that I don't people to follow my twitter account but I don't want to spam those people with tweets containing links they aren't interested in and about whom I know they won't be. :) Hence the need of groups.

I'm having a hard time seeing how using the search page (http://search.twitter.com/search?q=%23groupname) doesn't solve that issue.

Well, what about those who already _are_ my followers? Wouldn't they see each and every of those group tweets?