Build and Analyze -- the 5by5 Network podcast with Marco Arment and Dan Benjamin -- had an excellent discussion this week[0] on whether larger companies like Twitter and Facebook would acquire any of the popular "read later" services.
Paraphrasing, but Marco said that Pocket would "be acquired within a couple of years." Today's Spool acquisition, however, removes one potential buyer from the running. I imagine these VC-backed "read later" services might be slightly concerned today.