Has anyone ever purchased stocks early on for a startup that went IPO? Is this a wise thing to do?
There is a lot of academic research on this that you should look at.
For a company like LinkedIn with relatively weak fundamentals, one would expect the executives to purposely underprice the stock in order to generate a big first day pop because they are looking for an exit. So if I had money to invest, I'd probably buy at the opening bell and sell at noon. But don't take that as investment advice.
If you're not dealing in big money, you won't be buying from the underwriter at the IPO price, you'll be buying at the higher price (if you put in a market order), or not at all (if you put in a limit order near the offering price).
That's not to say that investing in an IPO is a bad long-run decision.
The executives typically are locked not being able to sell on the first day of trading. It also looks bad if they do sell.
It's the investment bankers that want to see a stock shoot up on the first day of trading. It's their clients who are the most likely to hold the stock for an hour and then sell it.