Semantic Web technologies, such as Linked Data and Schema.org, are used by a significant number of websites to support the automated processing of their content. In the talk, I will contrast the original vision of the Semantic Web with empirical findings about the adoption of Semantic Web technologies on the Web. The analysis will show areas in which data providers behave as envisioned by the Semantic Web community but will also reveal areas in which real-world adoption patterns strongly deviate. Afterwards, I will discuss the challenges that result from the current adoption situation. To address these challenges, I will exemplify entity reconciliation, vocabulary matching, and data quality assessment techniques which exploit all semantic clues that are provided while being tolerant to noise and lazy data providers.