In addition to the garden variety manufactured spend I do day in and day out, I also enjoy keeping my eyes open for new avenues that might prove easier or more lucrative. Naturally, most of those either don't work or do work, but cost too much to be worth pursuing. Here are a few examples in the latter category.
Reselling Marriott gift cards
There's a whole cottage industry devoted to gift card arbitrage, which consists of buying discounted gift cards and reselling them at a higher price or theoretically even the same price while pocketing any rewards earned on the initial purchase.
Remembering an Amex Offer from back in 2014, it occurred to me that you could manufacture unlimited spend by buying Marriott gift cards and earning bonus points on a card like the Chase Ink Plus, then reselling the cards below their face value.
And it would work! Except at the rate offered by Cardpool (currently the highest payout), a Marriott gift card receives just 88 cents on the dollar, meaning you'd need to get 6 cents per Ultimate Rewards point just to break even, or 4 cents per ThankYou point earned with a Citi ThankYou Premier or Citi Prestige card.
That's certainly possible with a premium cabin redemption on a partner like Singapore Airlines, but it's not even close to worth doing unless you're desperate to top up an account and don't have the liquidation bandwidth (or free time) to manufacture your points more cheaply.
Returning merchandise to a different form of payment
What if you could make a purchase with a rewards-earning credit card, preferably at a bonused merchant, then return it and send the refund to a different form of payment, like a non-rewards earning debit card or even a check?
That would be great, except for obvious and non-obvious reasons banks are extremely sensitive to returns or refunds from merchants where purchases weren't originally made. The obvious reasons have to do with interchange fees and the costs of processing transactions, and the non-obvious reasons might include concerns about money-laundering: a refund to a debit card would be a great way to deposit money in someone's checking account without attracting attention — which is why it attracts attention!
All sorts of stuff is plainly illegal
I've been living in my current apartment for 2 years, and an Oster-brand toaster has been living here with me just as long. I'm moving soon, and don't particularly care to haul a 2-year-old toaster across the country with me. If I were a thief, instead of a travel hacker, I could just order up a new one from Amazon, take it out of the box, send the old one back in the same back, and sell the new one on eBay.
But again, that would be illegal, so don't do that either.
I find that keeping my eyes open and walking through potential techniques step-by-step is worth doing, even when I find that a deal isn't ultimately worth pursuing. It usually isn't! But it's the rare deal indeed that's discovered by someone blindly following only the most-travelled paths.