Validity of heya-betsu so-atari

[Yoavoshimaru 0]

As I was reading the sumo FAQ, I ran across this rule (heya-betsu so-atari) that rikishi from the same heya cannot fight each other during "regular matches".  (I quote from the FAQ at this site)

So the question is, why is this rule around?  If two rikishi from the same heya were to fight, perhaps the oyakata could tell them who he wants to be the winner?  Or perhaps there will be animosity in the heya?

My thoughts next went to F1 racing, where it is routine to have two drivers from the same team (e.g. Ferrari) compete against each other all the time.  In F1, like sumo, the top prize is an individual prize.  However, F1 also has team championships which sumo doesn't have.  So it's not 100% similar but still interesting.  

Finally, a hypothetical question: what if two rikishi from the same heya have the same yusho contention record on the final day?  Must they face each other?  Or maybe in a playoff situation they'd have to face each other?

[Yubiquitoyama 4]

As I was reading the sumo FAQ, I ran across this rule (heya-betsu so-atari) that rikishi from the same heya cannot fight each other during "regular matches".

[Kotoseiya Yuichi 3]

So the question is, why is this rule around?

[Kotoseiya Yuichi 3]

I admit though that the result is that there will be some rikishi (such as some of the Futagoyama boys during the nineties) who will gain a lot in not having to meet good heya-mates.

And when these mediocrities get easy opponents and consequently lavish promotions, they are elevated onto a level where they are to suffer oxygen deprivation and get single-handedly manhandled by their own heyamates' worst opponents. :-D So it works both ways...

But I must conceal myself now as this is an eternity issue and something bitter debates are based on. (Arguing bitterly...)

I do agree ten (!!! ) makuuchi rikishi from a single heya was unnatural. (Feeling wacko...)

[Yoavoshimaru 0]

There's something instinctively disagreeable in the very thought as heya is a kind of a family.

One other example that just occurred to me is women's tennis in the past 18 months: Venus and Serena Williams.  They're sisters, yet they have to face each other many times when only one can win.  From what I've seen in interviews with them, they handle it well.  But I don't follow tennis that closely, so maybe I missed something there.

Anyways, to clarify: I don't think this rule is invalid.  I do think it's interesting when contrasted with some other sports.