It really depends on the situation. My SO's best friend (who is a friend of mine as well) has been with his fiancee for about 3 years. They got engaged after less than a year. Dating her actually made him a nicer person for a while. Then everyone found out how controlling she was/is. He started ranting about it to all his friends and everyone told him to break up with her. Some of his friends took it way too far and stopped talking to him because he wouldn't leave her. When he broke up with her about a year ago, everyone cheered, because he could buy things without her permission and could leave the house more than once a week. Then they got back together and she got pregnant within a month. Everyone held their tongue after that and he doesn't bitch to anyone anymore except me (because I never jumped to conclusions and realized he was just ranting, even if she isn't the greatest). It's getting harder not to say anything when all he tells me is that she never talks to him anymore except to tell him he's useless when his entire life revolved around taking care of the baby. I know it wouldn't do any good to say anything though.

My best friend though... that's another story. Her boyfriend (ex?) of 3 years is actually a decent guy compared to her previous boyfriends... but he's a total man child. He's a serious alcoholic who can't hold down a job and can't pay his bills (so she was paying for them). He didn't treat her well or ever take her feelings into consideration. He's also 30 and she's 21 and it really scares me that she's the responsible one. When they had issues, which was way more frequent than them being happy, I wouldn't tell her to break up with him, only ask if she was honestly happy with him. She always said no, but she loved him and couldn't leave him because she'd be less happy without him. They recently took a "break" (I call it that because she got all her stuff and said they were breathing up, but that they could get back together if he got himself together). I couldn't resist telling her quite a few times that it was for the best, and I know this will probably be an issue when they inevitably get back together.