[kaugesaar]

I wouldn't use the word likely. It might be because of who your target group is etc and I therefore have another experience. But yes, it does happen. The way it works is that Google allow themself to spend up to 2x your daily budget. If they exceed your daily x2, you'll be credited any overcharged amount.

Eg. Your daily budget is $200 and they spend $420, you’ll get a $20 credit.

Then there is the monthly limit, which is your daily budget x 30.4. Also here you'll be credited any amount they exceed.

[im3w1l]

So basically it sounds like the "budget" is actually more of a "target spend", that they will try to approximately hit in the short run, and hit very accurately on average over a month.

[em-bee]

what's the point of that? knowing that, why wouldn't i just set the budget to $50 and avoid the problem that way?

[username90]

Most likely the algorithms that chooses whose ad gets shown are optimized to not have to look up each persons spend for that day, as syncing that between all servers on every page request would be more expensive than all other steps combined.

I'm not sure how they could let you overrun by several times your budget for a day however, syncing these every hour shouldn't be a problem.

[tomaszs]

I have explained it in other comment above. Its not technical issue. Its by design