Other than betting systems and obviously BS like EvenBobs roulette delusions, I don't rule anything out as beatable with an advantage. Sports, Horses, tiddlywinks, it doesn't matter. You can oftentimes tell after a 3-minute conversation, or what someone says in their posts if someone is legit beating a game of chance. Even if you don't quite understand exactly what they are doing you pick up on things that do and don't make sense.

Occasionally, whenever there's something ambiguous such as handicapping there are a few people that it's hard to tell given omitted information. Eventually, they say/post something that puts them in the believable or the non-believable category.