Adam, good questions. In the seller's defense, he apparently only uses Keating - he also has a Greenberg card and a Spalding book for sale, both with Keating letters. I didn't look closely at Greenberg, but the Spalding looks good and it's a rather expensive autograph. I suspect that the Ruth autograph either has already failed PSA and/or JSA, or would if presented to them; hence, inappropriate for sale by any auction house.
As a sidenote, without the benefit of Mark's knowledge of the seller, I initially responded to him as I would anyone on ebay selling such a signature. After Mark posted that the seller was reputable, respecting Mark's opinion, I immediately contacted the seller with an apology. I know - unbelievable. All I will say is that any time someone refuses to accept a sincere apology, I write them off and at that point have zero respect for them until proven otherwise. So that was one-half of my research.
After reading Hank's response regarding Keating, who I only knew through a couple of interactions at the National and the autographs he was selling at his table, I googled him and learned everything additional I needed to know. Research completed and I have nothing else to say about either of the two people associated with this ball.
Regarding the ball itself - I ask again: $3,500 ebay price for a single-signed Ruth ball with a respected LOA? Why is it still available at such a steal?