Facebook exec to give speech later today.

FORTUNE -- Sheryl Sandberg is the keynote speaker this afternoon at Harvard Business School's Class Day, which precedes tomorrow's commencement. Talk about awkward timing!

Sandberg, of course, is chief operating officer of Facebook (FB). You know, the social network that allegedly warned certain bankers -- or, more specifically, it's bankers -- that its Q2 earnings would fall short of analyst expectations.

One week ago, Harvard must have been pretty psyched to have Sandberg (HBS '95) on tap. After all, her company was about to price one of the largest IPOs in history, with the only question being how high the shares would rise. Obviously she couldn't talk specifically about the offering due to SEC quiet period restrictions, but expectant MBAs would hang on every life and business lesson from someone who just helped Facebook bridge the chasm from tech phenom to Wall Street royalty.

How a few days changes things. Sandberg still won't be able to talk Facebook specifics, but she might need to make some other changes as well. After all, the company she helps run is now being accused of massive improprieties. Can she talk about virtues such as honesty, fair-dealing or competence without a disclaimer? Will the crowd be instructed not to giggle?

To be clear, I'm not suggesting that Sandberg doesn't personally hold those values dear, or that she personally did anything to violate them (only time will tell who did what, and when).

But I'd bet most anything that she wishes that she had declined the HBS invitation, so as to avoid having to thread a very narrow rhetorical needle today. And HBS probably feels the same way...

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