Given that frustration, activist investors have been considering whether to mount a proxy fight of their own to oust the Yahoo board, say people familiar with the situation.

That does not mean such a fight will break out.

And given the unexpectedly high level Yahoo's stock has traded at, potential activists who might want to build a large position in the stock have found themselves stymied.

The stock is down 15%, but the risk reward of mounting a proxy fight when you don't know whether Microsoft will be there if you win requires a stock price lower than this. (Video: CNBC's David Faber discusses what's next for Yahoo)

Emotions are still running hot on both sides of this failed deal. Yahoo announced that its annual shareholders meeting will take place on July 3, and notices from stockholders of nominations for persons to be elected to the Board of Directors must be sent by May 15.

Yahoo's largest shareholders told CNBC they would support a move to replace the board, given they feel that board let them down during negotiations this weekend.

On Friday, it was made clear to Yahoo's board that the largest shareholders would accept $34 a share for their stock. And given that Microsoft was willing to offer $33 a share, the expectation was that a deal would get done.

But in allowing Yahoo's two founders, Jerry Yang and David Filo, to negoatiate without the presence of advisers, these shareholders say they hold the board accountable for what was a predictable outcome.

While those shareholders won't embark on a public campaign, they would support activists, should they try to wrest control of the company through a proxy fight.

Still, the ultimate question--whether Microsoft is still interested in Yahoo after walking away--remains elusive.

Advisors to CEO Steve Ballmer say he has mentally moved on, while others who have spoken with him today say they believe he still considers Yahoo a strategic imperative.