I went to the US many times in 2009-2010 on VWP. I was working as a software dev with one of the largest companies in the world and wanted to hang out in the US to see a girl I liked.
I used to go 3 months at a time, sometimes one month, rent an apartment, work in the company's offices downtown. I straight up said I was there to see a girl and "telecommute" in the office with my colleagues back home. Never had a problem.