Get an anonymous Rav-Kav card if you care about your privacy, or if you cannot make it to one of the service points and prefer to buy a card from the bus driver.
A personal Rav-Kav card provides some benefits not available with the anonymous card. However, an anonymous card is still worthwhile, for example if you're planning to travel in the Tel Aviv area (Gush Dan) for a few days. In this case you can use an anonymous Rav-Kav card to benefit from 1.5-hour transfer tickets and from daily passes. Read more about fares and tickets in the Tel Aviv area here.
In Tel Aviv/Gush Dan an anonymous Rav-Kav card can be purchased from any driver of the bus companies Dan, Egged, Kavim and Metropoline for ₪5.00. An anonymous card never comes empty: you must load it with a daily pass or with some initial sum on the e-wallet.
Starting from September 2012, an anonymous Rav-Kav card can be obtained free of charge at all staffed stations of Israel Railways.