How is markup data processed and how soon does it appear in search results?
Data extraction from microformat markup is performed simultaneously while your site is being indexed by the Yandex search robot. Various sites are crawled with varying speeds that usually depend on the site update frequency. Additional information on the indexing procedure can be found in the Help topic on Site indexing.
For hCard, we recommend adding the pages that contain marked-up information into the Sitemap file in order to notify the robot that the specified pages are important.
Before being added to search results, the extracted markup data is usually moderated or automatically validated. The duration of these procedures may vary for different data types.
How secure is microformat markup?
Microformats are a completely open format. This means that you cannot control which services extract the marked-up data or how they will use it. However, you should keep in mind that any information published openly could possibly be used for malicious purposes. Semantic markup simply facilitates data extraction from text on webpages. The absence of markup in and of itself does not guarantee security.
In any case, it is up to you to decide whether you want to use microformats and which data to mark up with them.