Data access
Or when data API is made available for public data you have to access it through ludicrously niche methods such as SPARQL (instead of something far more commonly used, but not trendy, such as bog standard SQL)
.. Stares at lots of "open" UK data where access methods seems to have been defined by a set of SPARQL fanboiz/girlz rather than thinking what could be easily used by lots of IT literate people with minimal effort.
Caveat, yes I know there are lots of good things about SPARQL, but learning curve will deter lots of IT bods who might have had a quick casual "out of interest" play with the data & revealed something tasty if it was readily available using their existing skill set - you have to be a lot more dedicated to investigating the data to learn new query languages (especially when code tools for SPARQL are not exactly pushed by the big vendors e.g. MS are a big player in SQL so have a vested interest in NOT providing good SPARQL tools)