Yeah, few people from sythe buy from scam4fun because of poor customer service and just a bad record. As long as I have been here I have seen only a handful of successful trades and they are usually something small like 20m.
As stated above generally people buy/sell GP mostly from trusted gold traders on sythe as they have had more success that way.
I've seen countless threads about gold4fun and other sites like that scamming and so forth, its just not worth bothering.
The only GP sites you can trust are ones owned by trusted Sythe members. You can trust that they won't scam on their site because they will be banned on Sythe as well.
Personally I won't trust them because if you buy an amount of 100M+ they will most likely scam you I've seen a lot of people saying that they have been scammed by them but as ''Emperor_Nero'' said you'll only see only small amounts that are successful like 20M.