When we select our board house, most of us carefully consider space & trace, cost, turn-times and things like that. It's important to not forget about their capabilities regarding the silk screen layer. A great board can easily be made mediocre by poor quality silk screen. A Mediocre board can be made much worse. Ambiguous marking can make either difficult to use.
This board here has silk screen printed right on the pads. Mis-registration like this reduces the solder surface area and can prevent a good connection. See a little more detail in this post. The board house Sunstone.com has a service add-on to clip the silk screen off of the pads which would eliminate this problem.
Then, the ambiguity factor can be a problem with assembly too. Sometimes when parts are very close and the board house can't make fine line silk screening, we can't tell which reference designator goes with which part. And on polarized parts, especially diodes, the polarity markings can be ambiguous as described in this post. Diodes, especially barrier diodes can be a real problem with markation. A simple (+) or (-) just isn't clear enough.
weiße Zeug auf Silber Zeug ist schlecht