I don't know... but I've seen the tables. (I found an online copy of a fairly recent orthodontics textbook...)
Slight correction: When I said "pretty common", I didn't mean a majority of them failed; I meant that it's not an unheard-of problem.
From the first Google source I found:
"In general, mandibular advancement appears to be stable, if rigid internal fixation is used (Van Sickels & Richardson 1996, Dolce et al. 2000, 2002) (note by SirWired: "rigid internal fixation" refers to the titanium tie plates) and if anterior facial height is maintained or increased (Proffit et al. 1996). Several factors may affect relapse in mandibular advancements: the surgeon´s skills; proximal segment control, including condylar positioning and prevention of proximal segment rotation; prevention of counterclockwise rotation of the distal segment in cases with a high mandibular plane angle; the degree of mandibular advancement; and stretching of the perimandibular tissues, including skin, connective tissues, muscles and periosteum. (Will et al. 1984, Smith et al. 1985, Phillips et al. 1989, Moenning et al. 1990)."