[apowell]

I've never done it, but I suspect the easiest way to get "permission" (and I use the term loosely) is to add a section to your standard T&Cs, which customers agree to when they sign up, that allows you to identify current customers in your marketing materials.

[toast76]

I had considered doing this, but I get the feeling it wouldn't help should the company in question ask us to take it down. :)

[apowell]

Yeah, it's probably a bit late for that with current customers that have given you an explicit denial.