It offers you nothing of what buying shares of the company will (except when explicitly specified in the token sale) : no dividend, no voting power...
Expecting to earn money by buying tokens in an ICO is pure speculation, as you expect the token to go up. But this goes against the real user's will to use the service: they want a fixed price (who wants to use a service which price changes every day?)
To sum up, buy tokens as you would buy presales in Kickstarter, to support the company, but don't expect to earn money with it if you really it to be a real service / product. And avoid ICO that make you the promise of earning quick money.