Whatever. I'd like to offer my opinion at this time regarding what those who hold shares of Yahoo! at lower prices should do: sell into the euphoria. Yes, Yahoo! could still go up from here, and if that bothers you, obviously use a trailing stop. But if I owned Yahoo! on a day like today, I think I'd close out the trade. You just never know if the next headline you read is going to be something saying that the talks have broken down, Yahoo! is playing hard to get, etc.

Believe it or not, my gut is saying Yahoo! might go higher. Yet, if I held the stock, I think I would interpret today's price action as a late Easter present and take at least some of the money off the table. Microsoft/Yahoo!, Microsoft/Yahoo! -- whenever you think you'll never see that pairing again, that's exactly when the two-headed beast rears its ugly head. And I can tell you that I hope Microsoft never goes for a Yahoo! takeover. I just don't think that would be in the interest of Microsoft shareholders (sorry about that, Yahoo! shareholders). In my opinion, Yahoo! just wouldn't be the best partner, and it has had its difficulties; Brian White recently pointed one out.

The decision is yours. I certainly don't want investors to lose out on opportunity costs. But that's my thinking today. With Yahoo! up, at least consider cashing in some of the gains.

Disclosure: I own Microsoft and have covered calls written against the shares; positions can change without notice.