Apparently, VoIP services aren't completely blocked. It's just the ones that allow you to do cheap PC-to-Phone calls that are blocked, as it would kindof interfere with Etisalat's revenue. However, things like SIP and Google Talk, where it's just PC-to-PC works perfectly fine.
Flickr is blocked because Etisalat blocks "dating sites". That's the official reason. Yes, I know, flickr is not a "dating site"
In general, Etisalat's Internet service is pretty horrible compared to other countries. It's a well known fact. Sucks, but the people there generally just accept it and try to find workarounds (and doing that doesn't get them into trouble).