LinkedIn’s IPO, which is expected to price after the close of U.S. markets on Wednesday and start trading on Thursday, appears set to be a stunning success, but it carries a number of risks that may shake up investors in the future.

Potential risks include LinkedIn’s gutsy bet on future growth, an admission that it does not expect to be profitable in 2011 and the prospect of having its site blocked, which would limit its user base and could curtail some of the potential growth so attractive to investors.

After two years of losses, LinkedIn finally made money for its common stockholders in 2010 — but then it was back to only breaking even in the first quarter of 2011. A profitable company flatlining or swinging to a loss in its first year as a publicly traded stock could prove an unwelcome surprise for investors betting on the booming growth of social media companies.

On Seeking Alpha, IPO Candy says LinkedIn’s growth, positioning and financial performance in large part justifies their stocks filing range. But unless their future execution surpasses recent performances, investors will not see expected returns.

Takeda Pharmaceutical will announce the $12 billion purchase of closely held Swiss rival Nycomed later today as it seeks to expand in Europe and emerging markets.