A Google Places Help thread reports that when adding custom attributes to your Google Maps listings you get an error that reads "Your attribute value is too long."
An attorney trying to add custom attributes said:
I tried to add some the recommended custom attributes listed at URL for an attorney's Web site I'm working on. For "Years Admitted", "Professional Affiliates" , and "Law School" I got an error that reads "Your attribute value is too long." I got that error no matter what I entered in the field (even a single character.)
I have not tried to reproduce it, but Google Maps Guide Cecelia said:
Thanks for sharing madigrammedia. We're looking into this.
So something is likely wrong.
Forum discussion at Google Places Help.