pulmo

1) The process of content selection shifts from the user to the service provider, liability for copyright infringement also shifts because now they have influence over and responsibility for the content selection process.

2) The user of a content aggregation service is paying (directly via money transfer or indirectly by seeing ads) for the content selection, not only for the provision of an automated service to retrieve feeds. One could argue that the revenue the service provider creates with content selection is based on the publisher's content, the publisher therefore should get a share of it.

In that case the boundaries of freedom are not defined by the constitution any more, but by private parties. Therefore any constitutional stipulation of 'freedom of speech' is practically worthless. Freedom can not only be measured by the existence of a constitutional construct.

Yes lets ruin people's life for a tweet written in 20 seconds of mental derangement. Insane.

It's a classic negative externality. The costs for society are higher than the private costs. Therefore a market failure.