Just elucidating instead of replying on each of the posts. Though I may have my own personal reservations on the business model per se, they have been able to achieve something of a lot of value.
Time to market: There are established commercial relationships which have a lot of value. Recreating this may take years.
Cost of failure: Companies that got it right went through 10 times the number of mistakes while coming up with a successful model or technology. Larger the company, higher is the cost of failure.
Access to years of relevant qualified data: B2C companies have a lot of transactional history which has a lot of value for profiling users for up-sell/ cross-sell of other products and services.<