Would you guys elaborate please?
My view is a bit different:
1. Some groups are just posting (spamming) groups. people go in (or send a bot), post their ad, and go out. They don't read other people's posts, and they don't like/comment on other posts, etc.
So these groups
won't get you too much traffic.
But they will get you a little traffic. And that adds up when you scale it up.
So if you don't do it manually, and just send a bot to do it for you (so you just take 5min a day to set a bot to post to 000s of groups, and then the bot will do it),
it's not worthless. For 5min of
YOUR time (because you don't care about the BOT's time...), you get enough traffic from it.
2. Posting your URL in many groups can get that url banned, since some people will report it as spam.
So instead of posting your url, use url shortening services (bitly, and others).
That way, if many people report your url and FB bans it, it doesn't ban your real url, but your shortened url. So you just make another (new) shortened url, and start posting it instead.
3. There is a service that lets you shorten your url automatically using dozens of different url shorteners at once. VERY usefull for posting...
4. Many bots can spin text and spin url links. So if you spin the url, you won't be posting THE SAME url to many groups, and even if FB bans some of them, the others will still work.
5. Other groups are more like Forums or message boards (this is what wisdomkid called "active relationship kind of group"), where people actually read the posts and like/comment on them. But those groups usually don't allow posting ads and will delete the posts and/or ban you from the group.