No friends yet.
Jose, totaly agree with you and I actually prefer reciprocal way.
The elgg friendship system is not very logical itself and can be only use with friendrequest module. hope this can be introduced as option in the near future...
You can think of Elgg "friends" as a special access collection that you control and to which you want to grant special permissions to.
This is not really the same as the Facebook friends (which are reciprocal) or the Twitter followers (for the reasons you state).
Just because Elgg doesn't do things the same way as Twitter or Facebook doesn't make the feature a problem.
I don't see much difficulty with mimicking the Twitter followers though, because you can always make your content public and users have the ability to subscribe to notifications for any user or group they desire. Actually the Elgg system is better than the Twitter system as you can choose to make some of your content available only to specific collections of people.
My clients usually find the Elgg concept useful, but on occasion they want something else (usually the Facebook reciprocal concept) and as Martinez points out, there are plugins to do this.
In my view the friends user interface should be removed from core Elgg and instead plugins should be able to expose a variety of different options. This has been discussed on this Trac ticket here: