Microsoft Corporation (NASDAQ: MSFT) has been hungry for online advertising companies lately. Of course, the latest deal was a zinger: $6 billion for aQuantive (NASDAQ: AQNT).

In light of all this, it seems natural that Mr. Softy would buy Yahoo! Inc. (NASDAQ: YHOO). But Microsoft's chief advertising strategist, Yusuf Mehdi, threw cold water on this and said "[w]e have all of the pieces we need to move forward.''

What to make of this? I had a chance to interview Allan B. Krans, who is an analyst with Technology Business Research (TBR). According to him:

"I agree with the statement that Microsoft has all of the tools needed to be successful in the online business. However, a solid toolset alone will not spur an improvement in Microsoft's online business. Microsoft needs to drive online search traffic in order to attract advertisers to its toolset. For this reason, we believe a merger/acquisition with Yahoo! continues to make sense for Microsoft. Combining the two companies' respective shares of the online search market gives Microsoft the opportunity to drive search traffic and leverage its newly compiled advertising toolset."

I also got this from John Byrne, who is also an analyst with TBR:

"At this point I think maybe Yahoo is the stickler though - they've just implemented Project Panama and they probably feel like they're going to show real improvement over the next few quarters which would increase their value without an acquisition. Then maybe next year they're in a much stronger position."

Tom Taulli is the author of various books, including the Complete M&A Handbook and the EDGAR-Online Guide to Decoding Financial Statements.

Today (around 1 p.m.) ValueClick's (NASDAQ: VCLK) stock is up a healthy 15% to $34.50. Back in January, the stock was trading at about $23.

Of course, the betting is that this online advertising operator will get scooped up like its peers, such as aQuantive (NASDAQ: AQNT), 24/7 Real Media (NASDAQ: TFSM), and DoubleClick. Hey, why not?

The problem is that the mega cap internet players such as Microsoft (NASDAQ: MSFT), Yahoo (NASDAQ: YHOO) and Google (NASDAQ: GOOG) have already made deals in the space. Instead, the suitors that are left can't really muster the premium pricing. These companies include the likes of IAC/InterActieCorp (NASDAQ: IACI) and Time Warner (NYSE: TWX).

While Microsoft or Google may want to bulk up even more, the fact remains that this is pure speculation. In fact, ValueClick is a hodge-podge of different sites and is more a technology play. It's like 24/7 Real Media, which didn't snag a big premium on its deal.

So, as always, investors need to be very careful on this one.

Tom Taulli is the author of various books, including the Complete M&A Handbook and the EDGAR-Online Guide to Decoding Financial Statements.

There are a couple things that are typical with buyout rumors:  a) they are fun to talk about, b) the companies involved have lagging stock prices and c) usually the deal doesn't happen.

A recent piece in the New York Post speculates that Microsoft and eBay are in talks for a mega combination.  Sources?  Of course, they are unnamed (probably because of the federal securities laws, huh?) On the face of it, a deal with eBay would bring much to Microsoft: leadership in auctions, which is a cash cow business; a rapidly growing VOIP business through Skype; and a lucrative online payments business, aka, PayPal.

But, somehow, such a deal would probably fall apart -- say on valuation or antitrust grounds.

So, in the spirit of rumors, how about something more interesting:  eBay goes private.