When I quit CoH and moved to WoW, one of the big revelations was WoW's emphasis on the amount of content available after I hit max level. There was, for the average gamer, a myriad of activities one could do to improve their gear, such that one could feasibly never run out of things to do...unless you were a Grand Marshal/High Warlord in a Naxx guild with maxxed -everything-, which wasn't that common. My days of having a stable of high level characters to choose to play was over because I became time limited. Not playing my main character would put me behind in Honor in the old PvP ranking system as well as losing out on potential raid spots in tradechat pugs. For the first time, I encountered the opposite of consumable content: repeatable content. This was content that, if repeated, would give me benefits. I wanted to run BWL multiple times for Tier 2 drops. I wanted to run ZG for Reputation for my enchants. I wanted to do BG's for hours on end because I needed Honor.
When TBC came out, some of that repeatable content became consumed content and going back to BWL became a ludicrous concept for any reason other than nostalgia. Why? There was no incentive to redo the old level 60 content because there were no positive gains possible with the old content. However, one smart thing that was implemented with TBC was the revolutionary badge system, represented by the infamous Badge of Justice (BoJ) as a reward for killing bosses found in Heroic 5 mans. There were certain pieces of gear that one could buy for varying amounts of BoJ's, many of which were top level items at the time.
As TBC progressed, more and more 'badge items' were added to the list of rewards, some of which cost an obscene number of BoJ's. However, these items were somewhat on par with the then current top end raid drops. In addition, Blizzard made some tweaks and included the badges as a side reward for killing raid bosses. Even with this tweak, Heroic 5 man runs remained firmly entrenched in the repeatable content column as both new 70's and seasoned raiders could benefit from the gear. Karazhan, the introductory level 70 raid, experienced unprecedented popularity as it was, as raiders put it, 'an easy 22 badges', even over a year and a half after the release of TBC.
When WotLK (LK) came out, all of the old TBC raids became consumed content and this time, Blizzard introduced two levels of badges with two independent sets of gear, each purchasable only with their respective badge. One badge was achievable through heroic 5 mans and 10 man raids, and the other was a reward for 25 man raids. Initially, it would be assumed that the 25 man badges would be hard to get by people who were not in a large enough guild to accomplish that content (and therefor out of reach by the general population), but as more and more people attempted the 25 man content, they found that the initial assumption was completely false. 25 man raids were easy enough for the average gamer to accomplish and obtain rewards from. In the worst case scenario, one could do the 25 man Vault of Archaevon raid every week and have at least 1 piece of il213 gear by now. Unfortunately, while one can trade down a 25 man badge (Emblem of Valor) for a 10 man badge (Emblem of Heroism), in a 1:1 ratio, the opposite is not true.
So where do we stand now? Well, 3.1 will bring us a third badge, the Emblem of Conquest, with its own item list, all with a higher item level than the current available gear. In terms of repeatable and consumable content, for many raiders, much of the 10 man content has already become filed under the 'consumed' column. There's simply little reason to run a Main through Naxx10 anymore as most raiders will already have mostly 25 man stuff by now, unless it's for fun or due to obligation.
To make a few predictions, I see no reason for non beginner raiders to continue with Naxx10 once 3.1 comes out. Uld10 gear will be better itemized and have greater item levels and the Emblem of Heroism badge rewards will be relatively obsolete, if not so already. Additionally, once Uld25 becomes reasonably clearable by the average raiding guild, Naxx25 will then become obsolete. I also forsee people who have come late to the LK raiding scene or alts as possibly having a rough time gearing up appropriately to tackle Uld10/25. To compare, in TBC, latecomers or rerollers could run a billion heroics/Kara and get ~T5/6 gear and remain reasonably competitive. A little 'brute force-esque', but still effective.
The big question is: has Blizzard shifted their design philosphy away from repeatablility and closer to a consumable state on purpose or is this just an oversight? From the availability of the Bind on Account items, the fact that many of those Bind on Account items grant bonus xp, and my overwhelming urge to level my old Mage, I'd have to say that we have, indeed, moved to a consumer culture.
...but is that a good thing?
PS: Another Blue post regarding the difficulty of Ulduar:
It is not a huge leap up in difficulty from Naxx, but it is a step up.