There is a bug that gives rogues a PERMANENT 70% run speed increase. I was mind controlling this rogue in Ironforge the other day and this is how it works:
The priest casts Mind Control, the rogue just has to cast Shadowstep as mind control lands. Then if the priest moves you around as mind control fades you will appear behind the priest and have a 70% run speed increase until you use Shadowstep, Sprint, Mount or Zone.
If you change your run speed at all you will lose this effect. Latency causes this issue.