Is a 50K an "Ultramarathon"?

ul·tra   [uhl-truh]
adjective
1.
going beyond what is usual or ordinary; excessive; extreme.


I was having lunch with Jeff Browning today and talking about his upcoming 50K this weekend, which engaged me to make a quick "wise ass" remark. "Cmon, its just a 50K, its not even an ultra". And, this started our conversation.
Should a 50K be considered an ultramarathon? In short, my opinion is "no". I believe that a 50K should be in its own category, similar to half marathon or marathon but personally, I don't think it should be under the umbrella of "ultramarathon". Yes, I know that technically anything over 26.2 is considered an ultra. However, I don't consider a 27 mile race and ultra and I don't consider a 31 mile race to be an ultra.
Why? I think the skill set involved in a 50K (trail or road) is very equivalent to a marathon (trail or road). Racing these distances focus more primarily on pure, raw speed and being able to hold a hard but maintainable pace for 3:00+ hours. However, for me, when racing a 50K , all of the feelings, fueling, and strategy that I implement are pretty much the exact same as for a trail or road marathon. Okay, before anyone opens the flood gates on me, let me answer a few questions:
1. Do I think 50K's are easy? No.
2. Have I suffered mightily in many a 50K? Yes!
3. Do I think these are a less noble distance than say a 50 mile or 100 mile race? No.
4. Could you make a strong argument that this is the distance that I am the most competitive in? Yes.
5. Do I think they should be considered "ultramarathons"? No
6. Honestly, does it really matter? No. Not really. But its fun to talk about!
I think 10-15 years ago, there were not nearly as many "ultra" events. Therefore, it was natural to lump 50Ks with 50 and 100 mile races. However, now, there are hundreds of 50Ks each year and they can easily be put in their own category. However, again, to me, the difference between a 50K and a 50 mile race is two fold.
One is the mental side. It is fairly easy to train for the distance of a 50K. In fact, many people do 30 mile runs routinely every weekend as they are building up for their summer races. Therefore, the distance can usually be trained for and one can really know what to expect. With a 50 or 100 mile race, it is not something that is a normal distance training run (for most) and therefore, the body and mind are going to have obstacles that they haven't been able to tackle during training. Mentally, I always have mental hurdles to overcome in 50 and 100 mile races that I don't seem to experience in 50Ks. In 50Ks, it seems to be just much more physical.
On the physical side, in 50Ks, you can make mistakes and many times, you can ride them out with minimal consequence. In a 50 or 100 mile race, you simply cannot. If your legs, stomach, or anything else is shot at mile 25 of a 50 or 100 mile race... well, its going to be a long, long day.
Anyway, I'm not coming across to devalue the 50K. I simply think that it needs to be defined by its own distance and not to be "umbrellaed" by ultramarathon. That is just my own take. What do you think?