It says on wikipedia that "Flash of Two Worlds" came about because fans were complaining about the continuity discrepancy in Flash, where Barry Allen was supposed to have been inspired by Flash comic books he read as a kid. Of course, the Jay Garrick Flash had teamed up with Superman, but was a fictional character to Barry.
However, I find no official source that says that that was the official impetus. Actually, that seems to be the least of their continuity problems. How about the fact that in the Golden Age, Superman debuted as an adult, and they had since come out with the adventures of Superboy? Or the fact that heroes like Wonder Woman, Green Arrow, and Aquaman, had all had their origin stories rewritten in their own comics by that point. GA and Aquaman's were done through Flashbacks, but WW's adventures simply started anew as of issue #98. Then there's the whole issue of the fact that the Golden Age heroes had fought in WWII, whereas in the silver age, they were still young.
It seems to me it wasn't so much that there were all these "continuity errors" so much as that the DC editorial staff had already thrown all the Golden Age adventures into the bin of "didn't happen," or "not still in continuity." They had happened in a different comic book continuity. It seems to me that what Gardner Fox did with ""Flash of Two Worlds" was not to fix continuity errors so much as to take what was already obviously an alternate, defunct comics continuity,and actually bring it back and sync it with the current continuity. But I've always heard that it was "to fix continuity errors."
What do you guys think? Any historical sources I might actually look at to confirm any of this?