I am a US citizen - my partner is a citizen of the UK (we are not married). He is a consultant in the international development field so travels frequently, but often visits me in the US when he is not working. He has been to the US for visits of 2-3 weeks duration about 6 times in the last year. The past few times, immigration has hassled him about the number of visits he is making. We are concerned that one of these times he may be refused entry - is this likely?
He can be denied entry. UK citizens have the same options to work in USA as the rest of the world; typically H-1, L-1, E-1 and E-2 visas.