These satellites are going to damage real science that is already costing us billions (and what's more perverse, do it for a profit). Professional astronomers already warned us about the issue, and IMHO there's no reason to think we know better. Of course we're launching telescopes into space (like the James Webb, planned for 2021 [1]), but those won't be able to replace science done by the larger terrestrial telescopes.

For reference, the ELT, which is currently being built in Chile, will be 74 meters high, 86 meters wide (with a Ø 39.3 meters primary mirror), and weighing 5,000 tonnes.

[0] https://en.wikipedia.org/wiki/European_Extremely_Large_Teles...

[1] https://en.wikipedia.org/wiki/James_Webb_Space_Telescope