I see that "last-updated" is changed only when I add/delete images from album. But when I edit title or some other properties "last-updated" is not changed, whereas for images this is not the truth. Is this adjustable behaviour?
An album is "updated" with respect to its contents, several of the album properties can be changed without invoking this. What is considered an update is not adjustable. If I remember correctly, you can even replace an image within an album without modifying "LastUpdated"
The approach actually makes a lot of sense: Say for example a user decides to rename existing albums to fit a new name-scheme, or somebody comments on some pictures. You probably would not want it updated in these scenarios, as it makes sorting on date etc pretty useless.
On the other side, they could have made a user-control for it (do we have enough buttons yet?) to make some tasks easier, for coders especially. E.g maintaining a off-site copy of an account without using lots of time and bandwidth transferring everything.