Once upon a time, there was a poster of a young man fanning out cash in his hand. You could see one end of a $5 bill, one end of a $10 bill, and two $1 bills. He was also making a weird sign with his hand, like a gangster sign. The caption read "17 Dollars - Now that's gangsta". For whatever reason (some kind of misperception, most likely), someone poster'd that poster with the new caption "22 Dollars - You idiot" (or something to that effect). THAT poster was then poster'd with "17 Dollars - Duh" (or something to that effect). This kept being chained until the original image was not even vaguely visible. At times, the caption was not even related to the original image, but rather mere ad hominems or points addressing things said in earlier posters. This took on a small amount of infamy.

Thus, whenever a poster chain starts getting long, it's fun to remember "17 Dollars".