Challenges
The main challenge is for eID to be used in significant numbers by citizens and businesses. This is not the case in most EU countries, including Spain. Partly through lack of awareness and partly for design/technical reasons.
A related challenge is to move from the physical, or PC-based formats towards mobile solutions. Technical interoperability of eID is no longer a barrier. Legal (and political) interoperability is a bigger challenge. This needs to be overcome if we want to reap the benefits of STORK and develop an EU-wide interoperability of eIDs.