Bruno Lowagie, author of iText, says receiving small donations creates a lot of work – he'd rather have recognition:

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.

He did like Tipit's idea of combining lots of small donations into one big payment. I noticed he's put a Tipit widget on his website.