I was invited to give a keynote speach at IWWOST2009 workshop at ICWE 2009 conference. I've decided to talk about challenges of web engineering in building social web software. I will talk about service oriented architecture, I will discuss difficulties with current model driven approaches, and touch transactions a bit too. And all this of course in the context of two greatly succesful EU projects KIWI and idSpace :) where I work on this issues together with my IWIS team.