Open access entails online research outputs that are free of all restrictions on access (e.g., access tolls) and free of many restrictions on use (e.g. certain copyright and license restrictions). It seems as though many people are in favour of open access, as can be seen just by all the twitter accounts regarding the matter.
This piktochart presentation, however, discusses both the advantages and disadvantages of freely accessible content, from the perspective of the content producer.
Overall, I believe the advantages outweigh the disadvantages for a content producer. By making their work freely available online, they are able to increase their visibility, reach more readers, build upon other work and advance their career.