This is not an issue with anyone's HD. Bethesda announced why this was originally happening and previously fixed it, regardless of what you fail to see, it's a very real problem that has resurfaced.
Some instances it has been the individuals flash memory / hard drive causing the issue, so it can't be totally discounted, and I myself wont.
However, the texture issue and draw distance has been effected by the latest xbox patches as well, making it become a more common occurrence for people. I haven't had anything major in skyrim as of yet with the draw distance, I am seeing the textures being swapped for lowres, but I am noticing it showing up alot in other games now that never even twitched sense the patches for the xbox itself. Sure... it could be a hard drive... but... I own 3 xboxes, 3 different generations, and for all of them to experience the same issues across multiple games at the same time... your right, this isn't just a hard drive issue. While Bethesda had its own, now its worse, and more defined sense the last xbox patches many of the draw distance issues and texture issues can be related to hard drive read time, and memory. If there is too much going on, or some xbox background event is firing off, these issue will come up, expecially if your playing off the internal 4gb memory on the xbox, a flash drive or one of the memory sticks for the old xbox, as the hard drive takes presidents over the flash memory, and you have the speed of the flash memory itself.
For the flash memory to effect game play you don't even have to be using it, it just has to be plugged in, if you've got one of them that 'pulsate' or 'blink' while its being accessed watch it sometimes while your playing (any game) you'll notice there are background events accessing the flash memory.
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now onto the Nimroot bit, clones and other little 'glitches' people think are 'non-important'.
in general, after 100 hours, texture issues start popping up, after 200, people are complaining about the game lagging bad on them, draw distances effected, and random lockups. After 300 hours, place specific lockups, random lockups, degradation of textures across the world, draw distances greatly effected.
When these minor issues are left unchecked that consistently stack or duplicate, the problems for the player in the game will get worse, more quests will have issues, and the individual wont be able to complete alot of stuff. The pattern is there, if you watch the posts here, people are experiencing many issues within the same time frames for a single character. The more it goes unchecked the worse it gets. All of these "non-important" little issues add up, and eat up the system memory.