Over in ruljautonews
we have a translation
's latest entry where he details some upcoming changes to advertising on LJ. Specifically, a modified form of the self-promo block that's already available on the Cyrillic homepage will be made available to all journal owners, with all proceeds from that block going to the journal owner. And buried in the comments, Ilya confirms that Paid & Permanent accounts will see this ad, and that the ToS will be modified to reflect this.
This is a part of a larger scheme to increase ways for users to monetize their journal. Other announced changes are ways to pay or get paid for reposts, a paid feature to have entries float to the top of a friends' page, and the ability to cash-out earned tokens into rubles or dollars.