A post at AntiSocialMedia.net that's best quoted verbatim:

According to [former Novell chief scientist Jeff] Merkey, in 2006, Wales told him that in exchange for a substantial donation, Wales could use his influence to make Merkey's article more agreeable. Merkey made a $5,000 donation and hinted at the possibility of something much larger in the future.
Merkey claims, and the record confirms, that following his donation, Wales personally made several edits to the Merkey article, including a complete blanking of the article and destruction of its edit history.