Julian Baggini writing for the Financial Times and reprinted in Slate argues that atheists have a very strong negative public image in the United States out of step with other developed countries. As far as that goes, Baggini is right. But, it also understates the extent to which publicly coming out of the closet as an atheist, as I have, has grown tremendously less risky in the last three decades or so, in much of the nation.
In the early 1980s, this would have marked you as a member of the luntic fringe, together with people who wait outside fur shops to dump paint on fur coats and people who argue that the United States should have no Army, Navy or Air Force whatsoever.
These days, it is still a minority view and will still exclude you from the Boy Scouts of America. But, it isn't a view that will mark you as a person unsuitable for holding higher office within the Democratic party organization in urban areas (the secular left is one of that party's most reliable core constituencies), it has become a majority point of reference in parts of academia (e.g. the science and philosophy), and it is a view publicly advocated on billboards that raise little more controversy than the latest "I'm Mormon" campaign. It doesn't mark you as an outcast in many urban Denver schools where being a Chrisitan who attends church every week and actively participates in church activities is at least as uncommon as having no formal religious affiliation at all. In 2012, it is probably less of a breach of etiquette to deny the existence of a Judeo-Christian God than it is to deny the existence of Santa Claus or the Easter Bunny in the presence of children whose families you don't know well.
There are descriptors that are less likely to provoke a strong reaction, like non-religious, secular, humanist, or even Godless or heathen, and most of the time those are safer choices. "Spiritual but not religious," which includes atheists as well as other "softer" religiously unaffiliated stances, is the preferred description for an atheist seeking a date via an online matchmaking service.
But, the possibility of personal harassment, blacklisting and persecution from coming out as an atheist, has ceased to become a palpable fear. In the early eighties, coming out as an atheist (or as gay or lesbian) had been akin to publicly claiming Communist affiliations during the Red Scare, or being one of the first non-whites to attend an otherwise all white school or church, or to living in an otherwise all white neighborhood in the early 1960s. Now, at least in "Blue State America", it is relatively safe to come out. Your mileage may vary in parts of the United States where Country-Western music is the dominant presence of the radio, and the Confederate cause is still considered to have been a glorious one.
There is very little in the way of an organized atheist conspiracy, although an atheist lobby and some atheist charities have been developed in the last decade or so, mostly through the efforts of the American Humanist Association (a spin of from the Unitarian Universalists) and American Ethical Union (an organization with its roots in liberal Judaism). But, my generation of atheists has collectively picked up as part of the zeitgeist of our age the lessons of the Gay Rights movement. We have learned (just as the Mormons have) that going public and claiming your identity proudly, rather than accepting a socially imposed mantle of shame, can increase your social acceptability and your personal safety, for everyone in your community. It is a virtuous circle. Familiarity breeds acceptance and the more often people come out, the safer it is for those who follow in their footsteps. People are more likely to be tolerant of a community when they know a member of that community personally and they know that he or she isn't a bad person.