Are online networking services complicit in facilitating social change for the worse? In two empirically informed simulation studies, we give a proof-of-concept that the speed of networking and the amplification of network actors' relational preferences can have a profound impact on diffusion dynamics on social networks, essentially counteracting the benefits that should accrue from networking according to the strength of weak ties argument. Our findings can help understand variations in homogeneity of network neighbourhoods, i.e., in the degree to which these neighbourhoods act as "echo chambers", as well as the high context-dependency of success rates for a certain type of network intervention studies. They suggest that the general facilitation of connectivity like it today happens on the internet, combined with the use of personalisation algorithms, has strong and insufficiently understood effects on dynamic processes unfolding on the affected social networks.