Funny you should mention that. I'm Irish and white but my name (Eddy Robinson) 'sounds black' to a lot of people, and I wasn't aware of this until someone I was doing business with expressed surprise on our first meeting. I did a quick straw poll of acquaintances who I'd had first contact via email or seeing my resume and they confirmed this assumption. I can't say it's ever affected me personally though I wonder sometimes if it's a factor when I bid on a job and don't get a reply.
Indeed, and Mrs Browl has suggested I use this form professionally for a little extra sizzle, or even the Irish version (Eamon Mac Robin) for an exotic flavor - I work in the entertainment industry and even behind the camera personal branding carries a little more weight than in some other fields.
Other readers might be interested in this census document on the demographics of common US surnames; turns out there's a 44% probability someone named Robinson is African-American, for example: http://www.census.gov/genealogy/www/surnames.pdf
Jon Stuart Leibowitz decided that Jon Stewart was a better TV name. In America, we had had "Irish need not apply" signs in windows in the 1800s and early 1900s, but that prejudice is basically non-existent; if you think it'll give you a leg up, do it.
This article made me think more about the possibilities if I had picked some place other than California to live when I came to the US: http://daisysdeadair.blogspot.com/2008/04/on-having-black-na...