I imagine the High Elves don't approve of the majority of elves joining the Horde.

Because Blood Elves use fel energies to satiate their lust for magic, and High Elves don't...somehow...I don't really know. According to WoWWiki they meditate for at least 1 hour a day to try and suppress their magical needs, and that a High Elf can become a Blood Elf if he/she chooses to give into their need to magic.

Seems to me if that was the case then Blood Elves could in fact become High Elves if they chose to abstain from feeding on fel energies long enough to purge them from their bodies.

I think the main reason is that the High Elves see the Blood Elves as tainted due to their eating of other peoples/things magic. (Basically if High Elves ever became a playable race they would not have the same racial abilities as Blood Elves.) Since the loss of the Sunewell both Blood Elves and High Elves have felt their yearning and addiction to magic, but the Blood Elves have gone a little further to sate their appetites. Also the BEs have joined the horde while the HEs stayed pretty loyal to the Alliance even when the Alliance wasn't that loyal to them.

I think basically High Elves see the whole Blood Elf race as bing drug addicts (which in a way they are. Or were prior to the Sunwell Raid.)

Speaking of the Sunwell Plateau , has there been any follow up to what happened in the raid and seeing how it affects the Blood Elves? Are they addicted to the arcane anymore?

Nice Article BTW.

high elves hate blood elves because they used fel magic.

Something like this...

The High Elves see the Blood Elves as traitors who gave into their weakness and embraced fel magic. Along the way they have allied with naga, trolls, orcs, and even the undead(forsaken).

The Blood Elves think the High Elves have abandoned their people to ally with the humans that left the elven in their moment of need.

The Blood Elves followed a maniacal leader who would eventually turn around and screw over his own race. The Blood elves went to demonic magic in order to satiate their hunger for magic. The High Elves did not. They probably could make amends, but the Blood elves did a big no-no in the eyes of the High elves(demons are bad). So, they hate each other. Maybe one day they will come back together, but I doubt it for now.

It's not anything like that.

Ctrl-F on wowwiki.

"Her cousin Zendarin Windrunner, a blood elf who hated humans, tried to kidnap her children, as Zendarin believed the offspring of a high elf and a human mage would have a lot of magic power. "

It's personal only.

The elves of WoW have a very defined pecking order:
Night Elves think their off-shot ex-kin the High Elves are reckless for their use of Arcane magic.

High Elves think their use of Arcane magic is okay, but Fel magic like the Blood Elves use? No way.

Blood Elves think they have the situation perfectly under control, and point at the Wretched as the result of someone who doesn't.

The Wretched don't care, they just want more.

Are the Blood Elves still using fel energy to "calm the shakes"? I thought the whole Sunwell Isle/M'uru storyline had them finally rejecting the ways of Kael'thas and embracing the Light for power. Maybe that's just the Blood Knights.

Anyway, at this point I think it's mostly a political separation, kinda like how the High Elves split from the Night Elves. I don't think there were many (or any) warlocks in High Elf society, especially after playing with demons caused a lot of problems for them in the Sundering.

At present the differences between High and Blood Elves do seem to be mostly political, but there is some evidence that sucking down demonic energy was changing the Blood Elves as well physically as well. Most notably, the fact that their eyes glowed green instead of blue, and the existence of the "fel elves" in Magister's Terrace and at the Throne of Kil'jaden.

Whether the physical changes will continue now that the Sunwell has been reignited remains to be seen. We might end up with the race fractioning again, so we end up with the High Elves, the Blood Elves, and those Blood Elves who just couldn't get enough of that wonderful fel energy and think red skin and bat wings are a small price to pay...