Heavy WOW geekery incoming.
Today Blizzard announced their plans for Cataclysm raiding. Specifically there will be a single raid lockout for a dungeon and you will have to choose 10 or 25 man setting for your lockout. Also the loot across the two settings will be of the same quality, though 25 man loot will be slightly quicker to acquire on a per person basis.
Of course, the internet exploded. A mere 9 hours after the announcement came out the thread Blizzard created is at 166 pages and counting. I tried to read the thread earlier today and noticed that even though I was skimming through some bad posts and ignoring some truly bad ones I wasn't even keeping up with the flow - the thread was growing faster than I could read. Of course like much on the internet the posts were 40% 'This will kill WOW and Blizzard is a bunch of baby eating brigands', 40% 'I LOVE BLIZZARD' and 20% reasonable discussion.
The main objection to this change is of course that 'It will kill 25 man raiding'. It certainly won't *kill* it, but it will knock it down, stomp on its knees a few times and give it a good backhand slap. I don't think anyone can debate the fact that removing the prestige and "I'm the best because my gear has the biggest numbers" from 25 man raiding will get a ton of people out of it, but those espousing this point of view on the interwebs failed dramatically to prove that this is in fact a bad thing.
Everyone agrees that 25 mans are largely staffed by people who are there because of the quality of the rewards and that the bureaucracy involved is a huge downside. A small subset of the population actually loves the 25 man format and wants to continue doing it but they are dwarfed by the population of people who are there for the rewards. My prediction of what will happen when this change is implemented is this: Groups of people who really do want to be in a large guild with 25 players will stay there, as will a majority of the extremely hardcore players. The vast majority of people who runs 25 man content will stop doing so and will do 10 mans instead.
People really enjoy playing with smaller groups when the rewards are the same. It isn't feasible to make extremely hard content for 5 man groups due to composition issues so 10 mans are the sweet spot where 'as small as possible' meets 'big enough to make real challenges'. Providing more avenues for people to do what they like while still getting the rewards they want is both smart business and good game design.
You may enjoy the epic feeling of 25 man raiding, and I hope you have fun with that. I personally have something like 10-12 real life friends who really like playing WOW and are good so my path is clear.