Disc brake rotor size and forks strength I have been told that every fork has a maximum rotor size characteristic. For example, for my $75 Suntour this is listed as 185mm. The explaination that I have been given for this limitation is that any larger rotor will have significant chance of breaking the forks! That is, the braking force will be too high and the brake mount system will shutter.

Is this correct and precise information or is it just some legal insurance?
My guess is its not so much about the forks themselves breaking - I cannot imagine that sort of force can be generated by brakes when the forks themselves have to handle the forces generated in prangs etc that would easily exceed any braking forces..... Yep - forks break in a bad prang, but no one would buy forks that did not survive a moderate fall without damage

The failure point is most likely the mounting posts, or the wheel being loosened or even ejected by the brakes on a QR system (well known issue and one argument for through axles). 

However, the idea that bigger disks give more braking and bigger forces is overly simplistic. A cheap setup with 200mm discs ridden by a 100pound wimp will not produce the same force as a top quality 160mm disc ridden by a guy with the weight and strength of a gorilla.....  

I believe its most likely the manufactures covering themselves and weasel words to get out of warranty claims from guys who buy cheap shocks, put on the biggest brakes they can find and ride them on the biggest drops they can find - and then claim "It broke.......". The kind of guys that do this would not be seen dead on a bike with small discs.....