Judging from the small numbers of "active" posters present on site, a donation scheme will probably generate enough money to be a drop-in-the-ocean.
If admin is concerned about time spent and bandwidth costs, i'm sure that we'll all get to know about it immediately
As for anonymity, that's in our own hands. Paying monies over is hardly a guarantee against us "pillow talking" about the site. As for me, the only way my ex would find out about this site is if I told her or she perhaps hacked into my email account. Either way, a fee wouldn't prevent a malcontent from causing a problem here.