Weird thread. It's a bit old, but the most recent. I see posts about a solver, yet all that is shown is pictures of connect four boards on poorly played games with no demonstration that a solver is even involve in determining what moves went in or not. The lack of quality in the games give little credibility to the idea that one was used.
Anyways, from what I've seen these days, I haven't run into many, if any, cheaters even in 6x7 games. When I review my games, I often see one or more errors emerge, whether on one side or both, mistakes unpunished, etc. As for bigger board sizes, a solver doesn't seem like it would be very good. The expanded moves make it easy to go beyond the solver, and zugzwang is the primary win condition of Connect Four, which a a board that changes certain properties, such as whether there is an even or odd number of slots in a column, or whether there's a center column, will mess with how plays work.
