An article from the Norwegian Institute of Public Health claims that studies showing weight gain from artifical sweetener consumption are generally of poor quality, and that they remain silent about cause and effect.
It seems more likely that weight gain causes artifical sweeteners to be consumed than the other way around. It also seems likely that any lack of weight loss is caused by subconscious calorie substitution rather than the sweeteners themselves. Cutting calories makes you hungry.
3) You can never trust anything you read unless you know who said it. It's extremely important to be aware of who's talking when it comes to politics, science, religion and other hot-button topics. Any time anyone starts making interesting statements, it's time to check who said it, what their qualifications are, and how good their reputation is. As a general rule, boring statements are true, while exciting statements are opinions at best (and inflammatory lies at their worst).