Linze10, visa runs are generally pretty safe, but giving your passport and a visa fee is very risky. There are a couple possible reasons for the mixed experiences about Bangkok Buddy...
1. She might be busy, careless and just not see the importance of making sure people don't end up on overstay. Some might get lucky and really benefit from her services so not everyone has the same experience with her.
2. She might scam certain people, not everyone, if she thinks they won't do anything about it such as elderly people, nice guys, etc. In her mind, they're not Thai so it isn't that big of a deal to just keep certain people's visa money and not provide the service. It's known by a lot of people she likes to cut corners.
I'm not sure which reason it really is. All I know is that I had to pay a big fine because of her and got banned from Thailand 😞