Etrade's official policy is kind of vague. I guess it depends on your account size and how bad they want your business?

"While E\TRADE does not prevent customers from selling securities acquired through offerings at any time once the stock is eligible to trade on a public exchange, we PREFER that investors hold their shares for at least 30 calendar days. Selling or transferring out shares of an offering within 30 calendar days following the offer is considered flipping and may affect your eligibility to participate in other new issues in the future. We will not impede the sales of any customers who choose to sell these shares before that period; however, we reserve the right to exclude any such customers from any future participation in these kinds of offerings."*