So far it seems to perculate down to those who find advertising offensive BECAUSE it's advertising, and those who see the reality/immersion of it as a plus. Both perspectives, I totally empathise with.
To clarify, in my own mind I'd considered the real advertising around real tracks as the actual product, which I proposed to place in LFS. Thus, Valvoline, Shell, Cooper Tires, Dunlop, RBS, SAP etc would be the ads I'd consider to be genuine product placement because they're present AT real tracks, whereas online casinos, enlargement products (except Viagra, of course!) are irrelevent to the sport, not present as products (ads) at real tracks, and therefore wouldn't be what I'd consider to be ads we'd ever see in LFS. Fortunately, LFS being what it is, accepting advertising from such sources is unlikely ever to happen, because it's not in the spirit of LFS.. simulated realism.
Maybe I'm just a motorsport nut, but often I join servers not to race but to spectate. I just enjoy motorsport, and I do see the advertising billboards, as I would if I were watching the F1 GP.
Companies might consider a little extra investment to step into the virtual world. Since the majority of their audience is already principally seeing them on-screen in peoples' homes and since statistics bear out that people (at least here in the UK) spend more hours in front of their PC, these days, than in front of their TVs, it would take a fairly narrow-sighted marketing department to not see the benefits. And let's face it, how totally cool must a company be, to have their ads in a PC game like LFS!