Blockchain (may) make sense for these applications but did you stop to think if the applications themselves made sense ?
Lotteries, internet gambling and internet advertising are three cancers in my book, I have no interest in solving their problems.
Similar for non-currency exchanges (like synthetix) which provide a comparable ways to trade near-arbitrary assets, though admittedly that is less proven to be a clear winner so far.
1) Powerball seems fine and well. How do you make sure that the records on this blockchain were put there legitimately? (if you use crypto, you are saying crypto is the only use case) How do you generate a winner fairly?
2) Again, how do you make sure all the bets are on this chain? How do you know that all the bets are on the chain legitimately? How do you get the money in and out of this chain? (if you use crypto, you are saying crypto is the only use case) How do you fairly reflect the outcome so people get paid appropriately?
3) You are saying that you just want an ad network that is focused on making the minimum amount of money. The bigger problem with online ads is that most are never even viewed by real people. People don't need a blockchain to chase the $$. Either the advertisers sees results or not and then they stop paying. If a hoster doesn't make any $$, they try a different service to make more. They absolutely don't want to track money from the advertiser through X stops for each ad.
The good thing smart contracts are inspectable, so there is at least the open source aspect to help mitigate concerns.
The only gambling smart contract I'm aware of is the Mayweather/McGregor one, which broke because the API they used to report the win changed from reporting 'w' for win and 'l' for loss to 'W' for win and 'L' for loss, and nobody could update it.
Thankfully the author was trustable, after all, and put a refund method in it, otherwise it that money would have been gone forever. [0]
So, the use cases have been tried and they've all failed.
[0] https://www.removeddit.com/r/ethtrader/comments/6w5wcn/impor...
Which means any and all bugs or exploits are also law. And we know for certain that there will be bugs and exploits, which is why smart contracts are such an exceedingly daft idea.
I can't see why a blockchain would help here.
I don't like risk, but I do have recent experience with Internet "gambling" because the previous President of the United States of America persuaded his followers to bet that he'd actually won an election he lost, so I was able to make money answering trivia questions like "Did Donald Trump win the US presidential election in November?" (No).
Although there were some conventional bookies offering this bet, most of the money (as I understand it) went on exchanges, there were hundreds of millions of dollars in the exchange I used. On an exchange they're matching bids against offers, as you would on a stock market, you can either propose odds yourself or you can take the best existing odds somebody else has proposed on the other side of the bet. As with the stock market, when things are liquid enough it's possible to establish a small range of odds in which matches will occur right now, and over time that range changes.
It seemed to me that this offers everything you'd want, the assurance you'll get your money comes down to the institution offering the exchange, and its regulators, but it seems to me this would also be a problem for a hypothetical "blockchain" gambling system.
It depends what form of gambling you're referring to.
A blockchain based roulette smart contract could provide absolute transparency to anyone placing a bet. The exact process which determines the outcome is known, and it cannot be changed. The assurance that you get your money is the smart contract.
A smart contract based prediction market, such as Augur, can offer similar transparency. You have the assurance that, should the market be resolved in your favour, you will get your money. The main concern is the governance structure which determines the outcomes.
1. Running a lottery over the Internet. There are a lot of people who would be happy to buy a share in a typical national lottery as long as they could be sure they were not getting cheated. I don't care if e.g. 10% of the money goes to fund schools, as long as it's fair and transparent.
2. Internet gambling. If I bet on something, I want the odds to accurately reflect the bets of all the players, and I want to be able to get my money out if I win.
3. A currency for use in online advertising. A lot of the money that advertisers pay mysteriously disappears into the hands of middlemen before it gets to the sites that host the ads. There is also a lot of fraud. Having a transparent and accountable system would make it more effective for people who are not parasites.
Anything else?