[manyhats]

Yes, it's very uncommon (but not unheard of) to have large blocks of stock that aren't locked up in an IPO.

For SHOP specifically, 99.9% of the Class B stock (i.e., stock outstanding pre-IPO) is locked up for 180 days. (See underwriting section of the prospectus)

http://www.sec.gov/Archives/edgar/data/1594805/0001193125151...