I think this might be the first time someone had to suggest moving a post TO milesbuzz!

The answer to your question depends on several things:
-What destinations do you typically fly to?
If you fly to major markets mostly, you'd be surprised that most fares will be in lock-step amongst the majors. You shouldn't have to choose. If you fly to smaller markets, then you're stuck with whatever the regional carrier is in the area, and may need multiple FF accounts.

-Do you fly on short notice or with 14 or 21 days advance notice?
Again, with advance notice, you'll find very similar fares across majors and LCCs. Most fare differences appear on non-advance purchase fares.

-Do you ever fly internationally?
If so, the upgrades that come from consolidating your status will be very important.

-What are you looking for in a frequent flyer program? upgrades? free trips? that nice puckery feeling when they kiss your butt?
It all impacts whether you want to consolidate or not.

It works best for me to stay with one carrier, but many other split thier status across multiple carriers. I will say that I was forced to fly AA this week, and it was nice that I had some residual status there from a prior comp. I believe I lose that status at the end of the month, and I'll have trouble flying AA without it.