So, I've been reading a bit on epiphany on live.gnome.org and noticed, that you can block flash via user scripts. And since midori also support user scripts I loaded userscripts.org tried a few a lo!, one of them works exactly as I expect. Just go to Flash Block for Chrome, click install and save the opened .js file to ~/.local/share/midori/scripts/. It should enable automatically, if not, go to the Userscripts panel and tick it on. For it to start work, page reload is enough — there's no need to restart browser ;-) To whitelist youtube, just add 'youtube.com' to var exclude array at the beginning of the script. Supposedly it also works for silverlight, but as mono is banned on my laptop (no sound reason, I just don't want to use apps that they're in some weird language combo of java and c++ which furthermore need virtual machine running), I cannot verify whether this is true or not.
And on a completely unrelated note: I successfully managed to arrive at the hotel in Brussels I stay during LGM, and had a nice walk around the city with nicu ;-)