You are allowed into the US for business on the visa-waiver or the B1 visa (which is easy to get and is the default for non visa-waiver countries I think). But you can't _work_ there. It's a subtle distinction, and I suspect it relies on how the immigration official is feeling that day. Meetings, conferences, meeting investors, networking, etc, are all OK.

Doing the job you normally do isn't allowed, but it seems like it's pretty obvious that people do that.