Suppose you're responsible for a small or medium size Free / Open Source Software project. Suppose you need to keep your day job, because you don't generate enough money to live from your project (your product is useful, but it isn't mySql, jBoss,...). Maybe some of your users have mailed you to ask if they could send you a small donation.
In any case, that's what occasionally happened to us (the iText developers) in the last ten years. But... after accepting a couple of donations, we decided to tell developers they should use the money to have a drink on our health instead. Because there's just too much administration and overhead (payment services, banks, governments claiming their share of the donation) to make it worthwhile. A big "THANK YOU" in a blog post with a link to our project was more valuable to us.
Nevertheless, having some pocket money (to pay for hosting, books, a PC,...) is always nice. That's why I was charmed by an idea that was presented at the first BarCamp Ghent that took place last weekend. A couple of Dutch guys introduced a service called TipIt. The concept is that you can leave small amounts of money (10 cents? $1? 2 euro?) in different people's "virtual tip jar". When the total sum of tips you give is substantial enough to justify a payment, you pay. The same goes for the people receiving the tips: when a certain limit is reached, they are paid. Meanwhile, the guys behind the TipIt initiative keep the interests on the money that is "waiting".
That's a nice business plan, isn't it? This approach not only reduces the overhead in costs compared to using PayPal for every different payment; if you tip a site, you also get something in return: your name is mentioned on the site you tipped. Granted, this is a novelty idea and I'm not sure if it's going to work, but the guys who thought of this initiative really know what they are talking about. Check out their presentations on Voluntary and Free Economies.