I think regulations have changed over the past years, i've seen multiple girls going over 800 now. Unfortunately most still not very fake looking, but progress is progress i guess.
The regulations depend on the country.
The issue of volume mainly concerns pre-filled silicone implants.
Saline implants can be overfilled by the surgeon and they often do this to achieve a very firm result.
For pre-filled silicone implants, few years ago, many countries only allowed implants up to 800cc, for example the US Food and Drug Administration (FDA)
Even if ambitious girls asked for them, surgeons were not allowed to install them. Manufacturers therefore did not offer larger implants because it would have be impossible to sold them.
Now that the maximum volume is 1050cc in several countries and:
- ambitious girls ask for them
- manufacturers, as Mentor, offer it in their catalogs
- talented surgeons put them on
As they are pre-filled and often cohesive, there is also a problem with the introduction, you have to make a wider opening.