Habanerose: Don't think they intended for it to happen, but rather f*cked up their calculations (or just underestimated the amount of mass-buyers).
tremere110: How do you mess up calculations? If you know you are going to sell 10,000 games and every 10 games gives a freebie, shouldn't you have 1,000 games on standby for a worst case scenario? For the freebies to run out yesterday with the sale still going today means they grossly underestimated the freebies they would need.
Thing is, the more you buy, the less are required for the next freebie (10, 9, 8, 7, 6, 5 and only then it remains static):
Small Example of the math:
10 people buy 10 games each and everyone gets 1 freebie
10 x 10 = 100, which results in 10 freebies for 100 games sold
1 person (let's call him Mr. Whale) buys 100 games with each succesive purchase reducing the number required for a freebie by 1 until it reaches 5
10 + 9 + 8 + 7 + 6 = 40
60 / 5 = 12
Which results in 17 freebies for 100 games sold.
Which means a difference of 7 freebies for each 100 games sold... and to my assumption that GoG might have quite largely underestimated the amount of Big Buyers (don't automatically want to call them resellers or lump them in by default).