This specification defines an API for persistent data storage of key-value pair data in Web clients.
The use of the storage mutex to avoid race conditions is currently considered by certain implementors to be too high a performance burden, to the point where allowing data corruption is considered preferable. Alternatives that do not require a user-agent-wide per-origin script lock are eagerly sought after. If reviewers have any suggestions, they are urged to send them to the addresses given in the previous section.
More details regarding this issue are available in these e-mails (as well as numerous others):