As long as no one is actively trying to portray bitcoins as a subversive subculture, things should be fine. I've noticed that many forum members seem to view themselves as proto-monetary-revolutionaries, but I certainly don't look at things like this. If the public were to view bitcoins in a similar light, there is no way it can ever succeed. It's just commerce, guys. Free trade of the freest form, and nothing else. That might seem revolutionary to some in our modern world, but it should only seem that way to those whom have a deep vested interest in the status quo, and that is exactly the kind of person that we don't want to attract attention from. Nor are they the kind of people that tend to shop at Wal-mart, Dollar General or online most anywhere; and *certainly* don't buy anonymous phone cards for a pre-paid cell phone.
I don't know how to stop this entirely, but it was something I warned about on Freenet and some of the other peer to peer network discussions:
The number of "legitimate" uses ought to completely overwhelm by a large margin the "unseemly" or even "illegal" applications that may come from the use of that network. Freenet has, for instance, a very large amount of child pornography and other brazenly illegal content. Perhaps it has practical uses for things like sending messages between Chinese dissident groups, but the mainstreaming of that software is painfully slow and indeed a reason I no longer participate with that network. It certainly isn't "safe for work" and I nearly lost my job for having that on my work computer. Not because of the peer to peer stuff but because of the content and trying to rationalize the software as something other than a means to get illegal content... illegal meaning things beyond even copyright laws. Mind you, there are legitimate applications of the software, but when the "examples" are all subversive and attempts to offer content that is "mundane" are ridiculed within the community, it hurts rather than helps the cause.
For Bitcoins to really succeed as something actually used, stuff like the Heron store needs to be marginalized at best. I don't mind the anonymous transactions being involved here, but the emphasis ought to be put on freedom and legitimate otherwise legal transactions. I would like to work to get Bitcoins eventually recognized by an organization like Wal-Mart. I don't think you could stop the anarchists if you tried, so I wouldn't spend engineering development effort to kick that kind of thing off the network, but it shouldn't be a dominant feature. I would think that even those groups who want to engage in to more subversive acts wouldn't mind their traffic being drowned out by "legitimate" transactions.
As has been suggested by earlier posts, Wal-Mart isn't really an early adopter, so perhaps it would be better to go more for some companies that are more "hip" and into a network culture. The trick is to try and identify what companies might be willing to go that route.