Even through the AP/UB scandal there was never any evidence the dealing was rigged.
Sure, there were individuals using "superuser" accounts but that is something completely different.
Indeed, I've personally seen stats compiled by individuals who've recorded and scrutinised hundreds of thousands of hands on more or less every site and am yet to see any statistical proof of rigging.
The largest variation from the mean I've yet encountered (on a meaningful sample) is less than 0.05%...in other words virtually none at all.
The closest comparison I can come up with is the WSOP
Main Event two years ago when a player was chatting to Joe Haschem after they kept hearing moans and groans from bad beats around the room. And his response?
"With this many tables you're going to see a lot of that today".
The bottom line? Go to a card room or casino for ten hours and count the number of times bad beats and unusual cards are dealt. Then go home and count the same thing on an online table in about 40 minutes. It'll be about the same and the ratio is probably quite close.