Apparently you can NOT increase your mount speed above 10% of the listed amount no matter what you use in enchants / items / buffs. This is to answer the question for all you people asking about the [wowitem]Riding Crop[/wowitem] stacking with other items / enchants.
[blizzard author=Drysc link=http://forums.worldofwarcraft.com/thread.html?topicId=74339557&pageNo=1&sid=1#3]There's not any current intention to allow either on-foot or mounted travel to be increased by items beyond 10% that each type of travel already allows. So regardless of what you have equipped you're not going to get above 10%. The riding crop is really just a one stop replacement so you can clear out some space you might have been using for other speed increases. Hey, there's the bag space solution you've been wanting! Enjoy. ;)[/blizzard]
wat about Crusader Aura + [wowitem]Riding Crop[/wowitem]?
now that would be funny...lol