Hi Helen
I've been researching (my) Ridout family for about 12 years now and branched out into looking at other families of the same name in the area. The further I went back in time it became apparent that there are probably only three actual, unrelated dynasties; this seems to have been confirmed by the results from a Ridout yDNA project which I set up, although who knows if non-paternal events have concealed actual relationships?! Anyway, two families seem to have originated in Dorset, specifically in Sherborne and Blandford; a third Ridout clan descended from the illegitimate son of a noble Devonian man who held territory in nearby Henstridge in Somerset. So, this is why you're tripping over evidence of Rid(e)outs in so many of the towns and villages as they slowly expanded and move away from their origins. Nowadays there are probably more Ridouts living in the USA and Canada, descendants of successful early migrants. Personally I believe that the majority of the online trees that you are talking about are inaccurate in one way or the other but that is just my own opinion :-)
Cheers, Karen