[PaulHoule]

It's definitely true that accounts above some threshold ($1000?) get extra scrutiny, not just from a adsense perspective but also from an seo perspective.

In the long term, Google would be happy to replace the open web with Android or Google+. In the short term if you compete with Google images or other Google properties it is open season.

[poopsintub]

From what I've read, they do a manual review at certain times right when payout is due. I've seen bank transfers for months on a certain day or within a day or two. But when I had a jump in earnings, it took 3-4 days longer.

[tomkarlo]

That's a fairly common anti-fraud pattern for lots of systems: if a particular account's performance exceeds its long-term trend by a large amount (say 100% or more), it gets flagged for manual review. Once a payment goes out, it's not economic to retrieve it, so you want that extra review to happen before it's issued.

Ideally this would cause a delay in the payout, but if an account doesn't break the threshold until just before the payment date, the review might cause a delay.

This is common on ad platforms, credit card processors and even auction platforms like eBay. I would guess that it's a "standard practice" for risk mitigation.