There is certainly a lot of anecdotal evidence to suggest that a standard lock-up of 6 months helped protect stock prices from wilder swings from rapid sales.
What’s more interesting to me at least is Spotify’s recent, hyper successful IPO. There was no lock-up at all for employees or traditional investors (there was a small exception for a strategic investor).
The result? A great IPO and no issues with 5x–20x the immediate liquidity of a traditional, locked-up IPO:
Spotify of course is a brand name that can drive significant float, with a long financial track record. Most IPO’s in tech are of companies a stage or two behind, or at least, historically it has been the case.
But Spotify does seem to suggest a lock-up may not be as necessary as some thought. And letting at least some employees shares out early IMHO is a good thing.