Never seen it for ball pythons Mykuhl. Seen it for other species and it's well beneath the 10 to 15% ratio.
Eric, I've seen a lot of over feeding related health issues in many species of snakes. Some snakes do not metabolize high levels of fat very well and form lipomas or liposarcomas in a fairly predictable pattern if overfed.
Considering that ball pythons - especially males - climb and feed on birds, we could probably hypothesize that the average tupperware-housed male ball python fed 15% of his body mass weekly in rodents is tracking quite a bit above what he was designed to take in considering the lack of activity.