This is precisely what seems to have happened today and let's be honest, this sort of incident has been brewing in the sponsorship industry for some time and it's the kind of story that makes the whole industry look ridiculous.
The reasons for the ban on frites-toutes-seules, one can only assume is to protect McDonald's sponsorship rights, for which they've paid an exorbitant amount of money. It's too early to know whether this "initiative" has been driven by the sponsor or by the rights holder (in this case, LOCOG) in an attempt to curry favour with their fast food partner but either way it's a huge own goal for everyone.
Let's try to remember why we sponsor in the first place. I've blogged extensively about putting the target audience first, yet too often their requirements become the last consideration in the scramble to tick every box in the contract. As an industry we have to get better - and fast - at balancing the need to protect commercial investments and alienating the very people we're trying to engage with. Common sense needs to be applied to ensure that we all know at which point on the "continuum" a positive experience becomes negative, allowing us to consider the bigger picture and prevent ourselves from looking silly.
More here on sponsors not quite getting it right (and some who do!)
For those of you who haven't seen it before, here's the Eddie Izzard sketch. I hope it helps to illustrate my point. Even if it doesn't, it's bloody hilarious.