It's a difficult balance, though I think most open source projects are too modest in asking for donations, which, fair enough is pretty uncomfortable at first. You can definitely be too in-your-face, like Jimbo Wales is the sad-eyed picture of taking this too far sometimes.

Thing is that explicitly asking for money works, it gets results. If you can get people to pay money to watch you screaming at video games on Twitch, you can definitely get people to pay money for working on useful software.