> No really important to have an id (performance improvement is marginal).

What if some frameworks/libs we use had CSS rules for `.logo`?

In http://stackoverflow.com/questions/544010/css-div-id-vs-div-class the best answer says "In general, use id whenever you want to refer to a specific element and class when you have a number of things that are all alike. For instance, common id elements are things like header, footer, sidebar. Common class elements are things like highlight or external-link.". This totally makes sense to me. Doing otherwise is not good design in my opinion.