Why do we still have servers?

I was wondering about it all day yesterday, considering the existence of cross-realm play, CRZ, that PvP, dungeon finder and LFR all pull across multiple servers why do we still have those servers at all? Are they a relic of the original game's design? Are they still physically necessary or could we simply have all these different servers exist as one large super-server that everyone in a region plays on? It certainly feels to me that, for better and for worse server communities are a thing of the past - I know a lot of people who play WoW, my friend's list is relatively hopping and my twitter feed even more so, but I haven't run a dungeon with random people on my realm since mid-Wrath and even then I didn't do it very often. Before the rise of dungeon finder groups, I either ran with a guild group or I didn't run, having soured on the experience after tanking BC heroics.

The way I currently play, I raid with my guild, run LFR occasionally (not very often) or queue for some dungeons either solo or with some Real ID/Battletag friends, do some retro raiding in the same fashion, and in general to me my server is almost completely meaningless. I play with and chat with people from all over the place, from Sisters of Elune to Norgannon to Malfurion to Kilrogg. If I could add EU players and chat with them, I'd have an even bigger friend's list. The people I know in game are people I've played with, people I've chatted with online for a while, but in very few cases are they people I've actually met here on my current server outside of guilds I've joined.

Of course, as I've argued before, personal experience isn't universal and anecdotal data isn't conclusive. I'm just one player. So the question becomes, what about you reading this now? How important is your server to you? It's very possible there are thriving server communities out there that would be damaged by a change that reduces server identity further and if so I think it would be useful to find out. If a single mega-server per region would be detrimental to people's playstyles, let us hear you. Positive or negative, your feedback is desired.