Prior to
sueing, someone with a bit of initiative could send an
invoice. I suspect many companies, when faced with an actual invoice
of some reasonable amount (<$1000) would simply pay it. Some text to
the effect of "You didn't contact me before using my text. However,
I'm willing to grant a retrospective licence for $.... under the terms
at my website [...]".
Will the WMF let me keep half the proceeds? ;-)
It's nothing to do with the WMF, it's not their content. The people
that wrote the articles need to send the invoices.