There are several purposes for proper and trustworthy tracking of individual's publications. Whether we as researchers like it or not, we are gradually more and more evaluated on the basis of our publications output. That is, our grant applications/proposals and other means of funds acquisition are rated, at least partly, against our publications track and a future projection thereof. If you want to convince the hiring, or grant committees and other fund holders, you show your list of publications. The more trustworthy, the better. Hence a reason for a centralized trustworthy publication tracking service. Also, people change names (e.g., by marriage), affiliations, sometimes fields. Proper attribution by automatic algorithms, such as those at work at WoS, Scopus, Google Scholar, or Microsoft Academic Search is therefore unreliable. Having a real-world and trusted tag which I could use e.g., on my papers to identify myself among the hundreds of John Smiths is useful.
1) What are the interest of using an unique digital identifier as a researcher?
- trustworthy disambiguation
- central trustworthy register
- semi-automatic tracking of publications, which however should be customisable by the ID owner to fix all the mistakes/misattributions
- citation attribution - often e.g., WoS, attributes citations mistakenly to wrong people, because people make mistakes in references/bibliographies, etc. A central register can help with that.
2) Is it commonly used in the scientific community (by publishers, databases, commitees)?
If your name is unique, it's easy for the committees to check your track by simply googling you, then these guys don't care much. If you are John Smith of this world, than they are not able to do that and would ask you to prove your track record. And that can be painstaking. Even with just few dozen papers published, I myself am not able to get my WoS record correct. So to set the answer straight: currently, not many people use it for other than personal purposes, but many (including myself) hope, ORCID will succeed and the academic community will start to use the scheme and life will get a little bit easier.