Presumably by 'tourist visa', OP means the visa waiver program (at least for people from Europe/Australia/etc) - you can enter on this if you're visiting on business. Where business stops and work ends seems like a difficult question to answer.
He's from India, I expect he means some sort of genuine tourist entry visa. Never been to the US, so I don't know about its visas, however.
I'm from the UK - meant the VWP :)
Thanks for the replies everyone
Oopsie. Got confused with another HN story, my bad!