"People who get to earn the equivalent of a CEO of a Fortune 500"

This somewhat relevant because witnesses do more than run a node, they are also part of the governance process of the network by deciding which versions to run, generally providing input to the developer team, and serving as a conduit for representative stakeholder influence over the direction of Steem. In the great debate over the curation rewards (8.2/8.3 debate), witnesses were called upon to decide which version to accept going forward. The developer team frequently requests input and feedback from witnesses on the content of upcoming releases.

Thus you I suggest that one should choose witnesses not only based on whether blocks are signed, price feeds are updated, the money is channeled elsewhere, etc. but also based on the experience, expertise, judgement, vested interest in the success of the system, and character of the witness.

The Steem ecosystem is now approaching $500 million in market cap and while we may not quite need 19 Fortune 500 CEOs worth of qualifications yet, there may well come a time that 19 witnesses of that stature and caliber would be the best thing possible. We certainly do want highly experienced, highly vested, and highly capable witnesses who are best suited to represent the diverse interests in the Steem ecosystem and make excellent decisions about what makes a blockchain successful, not just server jockeys and grant administrators. Those sorts of qualifications do not come cheap, and if there is too much focus on witnesses as pass-throughs for money, then it will turn into a race to the bottom on compensation and the best qualified by the above criteria will certainly drop out.

Whether all of the current 19 full-time witnesses are the ideal people for the job is something that the voters can decide. My personal opinion is that there are too many witnesses who are there primarily or entirely by virtue of their history with the Bitshares community, and I'd like to see at least one or more from the blogging/marketing side, though last point may be a bit of a challenge since the job does also require experience managing security-critical IT infrastructure (either directly or managing other people to do it). That combination may be quite scarce.

Finally one should not dismiss too easily the costs of the actual infrastructure as Steemit continues to scale up. How much do you think Reddit spends on servers, etc.? Well each witness is something like 1/19 of the backbone infrastructure of Steemit and will be eventually be spending something similar. (Already the costs to run a good witness node, along with associated seed nodes, including redundancy and headroom to not fail in the presence of viral growth, are not trivial.) One of the witnesses (sorry I don't recall which) has stated his opinion that each of the 19 witness slots will over time evolve into significant businesses each managing a data center and significant staff. If so then in addition to the above qualifications, witnesses also need to possess the capability to manage all aspects of this sort of rapidly-growing business without major mishaps, mismanagement, and down time. Again, you do not want the best qualified to drop out and leave the network in less capable hands.