The only record I've seen is this in Europe.  I've seen no evidence they've actually used the mark in commerce as a mark indicating products unique to Gox.  Generally, a trademark must identify the products of the specific entity claiming ownership of it, and that entity must have control over the use of the mark.  Gox has effectively abandoned the mark by never attempting enforcement, not that an enforcement attempt would have been likely to succeed.

I suppose it's possible an intellectual property troll will somehow end up with possession of whatever rights they have in the term, but I wouldn't worry about it much unless it actually happens.

The trademark registration does not register actual ownership of a mark, but merely puts the first filer (in most jurisdictions) basically "first in line" with their claim of ownership, such that an accused infringer does not have a defense of lack of notice.  Of course, this being a registration in Europe, Gox would have to be able to demonstrate that it actually used this mark in commerce in at least one EU country.  And of course laws vary by jurisdiction so the exact impact of their use in commerce, assuming it exists at all, might vary in unpredictable ways.