So...there are a bunch of problems with this movie. The file shouldn't have been left for Meg to read. Meg shouldn't of read it. Truthfully this is a terrible way to get information out and to get the information you need. I would like to think that in real life, outside of Hollywood, journalists and policemen aren't as unethical and careless. There is a problem with tape recording without the knowledge of the person. In some states, it's illegal. In Utah, the law is that only one person who is being recorded has to know about it. So as long as the reporter knows, the reportee doesn't have to be told--legally--not ethically.
Another problem that has been mentioned in other posts in how Meg seems to become a romantic interest to people that can give her information. It's true that may not be ethical, but I don't think there is a journalism ethics problem here. It may simply be that she doesn't associate with many other people that don't profit her newsroom goals. Sure the detective could give her information, but is it really her fault that he likes her? Or that at some point she may have liked him? I also think this wouldn't be as much of an issue if the situation were revered and the reporter was a man and the source a woman. I don't think there would be as much of a problem if a guy, who has gone out with a girl several times for whatever reason, gets romantically involved. In fact, this reminds me of a Robert Redford movie, except Redford was a lawyer not a reporter, but the concept is the same.
Anyway, back to journalism ethics. One of the things that surprised me was the newspapers attitude about what to print. They were only concerned with the legal boundaries imposed rather than joining them with a little ethical reasoning. Truthfully, if I were the editor of that paper, I wouldn't have ran the story until Meg had gotten a hold of Gallagher. The story wasn't that time sensitive so it easily could have waited at least another day and Meg could have given it a good try. The story would have a more fair viewpoint and at least given Gallagher a chance to say, "Hey! I have no idea what you're talking about," given him a chance to keep his business going maybe, contact the workers union and so on. Plus it would have made Meg look more like a professional when Gallagher came to see her. If there are holes in your story you really can't say you are pro at reporting.
Another problem with the paper's lack of ethical responsibility was the attitude it took with the abortion story. If Meg was paying attention she would have realized there was a little more at stake here than simply Gallagher's alibi. Gallagher obviously knew he had an alibi and clearing his name was important to him, but not as important as the mental state and social appearance of his friend. There are other ways to write that story to without mentioning the abortion. I think that could have been handled in a way where the consequences would not be so drastic.