I've seen lately a few posts celebrating a streak of days with more power ups than power downs. The paused programmatic STEEM sale of Steemit, Inc. most likely helped reversing the trend.
But even so, there are different kinds of power ups and power downs.
For example, you can power up your liquid STEEM rewards. In almost the same category, you can exchange or convert SBD to STEEM and then power the latter up.
In a second tier category, you can sell something for STEEM (product, service, digital asset, SE tokens, etc.), then power up. This type of operations also give some boost to the Steem economy.
A "premium" power up in my book is when you buy STEEM off the market and power it up. In this case you bring more money into the Steem ecosystem.
For the power downs, the situation is even more complex.
The "fake" power down. I am doing that on all my accounts but one. To someone who doesn't know what to look for, it looks like a normal power down.
You may think: Aha, why should I trust this guy? He is powering down!
But it's easy to check really. In the image above (screenshot from SteemWorld, obviously - Balances tab) you see a button "Outgoing Routes...". If you click it for my account 
Which means that all the withdrawals from the power down go to my account 
Anyone can do that obviously. And that's NOT a real power down, that's moving your stake to another account of yours. Sure, the same process is used for security reasons.
But that's why I call it a "fake" power down. Sure it goes to the other account as a power up too, so the power up/down stats should be ok. But what if the owner doesn't tick the "receive vesting" checkbox and powers up manually when he or she remembers? There might be a delay between the power down and power up, but still ok.
Power down to pay for Steem-related expenses. Well, most witnesses do that. Steemit, Inc. does that (or did until last month and probably will do it again).
Power down to buy something in the Steem economy. If someone powers down to buy a strong collection of Steem Monsters cards he or she wants, is it right or wrong? SM is still in the Steem ecosystem. And those cards are tradable. And they produce more gains. Just an example. I wouldn't power down for that, but I don't even have enough SP.
Power down to have trading liquidity. Some may think this is bad. I don't. There needs to be a balance between available/tradable STEEM and blocked (powered up) STEEM.
Power down to exit. Whether full or partial exit, you can't tie somebody up if he or she wants to leave.
Power down to extract pennies. I don't believe it has an important impact on Steem unless the user spams with low quality content or plagiarizes. It has however a big adverse effect on the accounts which do that, because they never grow and will never earn more than pennies.
In the power up and power down stats we add these numbers up and see which is greater than the other. But there can be a real story behind every power up / power down. How relevant it is to add them as if they are the same?
