I see, I misread your reference to Reader 11 to mean you were using Acrobat 11, but it looks like it worked out anyway.
The base-14 fonts are special in PDF because they are guaranteed to be available even if they are not embedded. If you select a non-base-14 font for use with a form field, the entire font usually gets embedded, since each glyph it contains has to be available for use with the field. This can take up a lot of space if you do this a lot, and the space isn't reduced if you change back to a base-14 font later because the internal reference to it is not removed. This is caused by the bug I mentioned.
In your case, however, the entire font doesn't get embedded because fonts like it (e.g., large asian fonts with a lot of glyphs, Arial Unicode) would take up too much space if fully embedded. If it did, a 100KB PDF could bloat to 20MB with that one change. Instead, users are expected to have such fonts installed on their system, which is why you were prompted to install the font pack. This despite the fact that the font was not actually used by anything in your document, it was simply the orphaned reference to it that triggered this. This should get fixed in Acrobat eventually so this type of thing doesn't happen again.