The Fine Print
Add this to your rules of thumb file:
When designing something (anything), if it doesn't cost you (in terms of design, brand or functionality), then always use bigger type.
I just wrestled a Linksys router to the ground after an hour. On the back of the router, the IP address and password are embossed in 8 point silver type (on a silver background). The cost of making it twice the size: zero. Same with your instruction manual, the emergency instructions on your airplane or the menu in your restaurant. The CD player I just tried to use has the same problem... the numbers on the inside of the player are tiny, black on black and unreadable.
Style matters. It's a big part of design. But at some point, style fails part of your audience (and I'm under 50!).
[PS I did live chat with Linksys and Rosell was amazing. Problem solved. Recommended.]