That is not the normal experience of people who exploit SIA's poor lines. I lasted for years (due to bad luck) until I finally won $20K and had my account closed. They banned me and sent me a check for my remaining balance. Many people have had this same exact experience.
I would bet the max on NFL games where I was getting +7.5 -105 when Pinnacle had +7 -115. I would bet boxing matches where the other side was arbable by 10%... I am talking bets where you are just blatantly taking money from an incompetent bookmaker (in the long run).
Were you and your friends all betting the same stale lines (sharing info)? It usually takes SIA years before they figure out that someone is betting their stale or rogue lines, so something you did must have brought you to their attention sooner. I am not saying you did anything wrong, just that SIA usually takes years, not weeks, to realize that someone knows what they are doing.
Also, SIA is head and shoulders superior to BP. They have better software and are much more trustworthy. And did I mention they have the weakest lines of any book you can count on to pay winners?
If you have a chance to play with SIA, definitely take the opportunity. Try not to draw attention to yourself though. Don't bet the max, don't tell the world about the stale line you found, etc. Eventually they will find out that you are an advantage gambler and give you the boot, but they pay.