As Yahoo (NSDQ: YHOO) shares have shot up over the past two weeks, Microsoft shares have gone the other direction, putting investors with stakes in both companies in a tricky position. Early on, we noted that one major Yahoo shareholder, Capital Research, met with Microsoft CEO Steve Ballmer to gauge the value of its Microsoft holdings would not go down more than its Yahoo holdings would go up. TechTraderDaily notes a report from Institutional Shareholder Services that finds that most of the top 20 holders of Yahoo also have holdings in Microsoft (NSDQ: MSFT). And most of these have more invested in Microsoft, so in all likelihood, they’ll be pressuring Yahoo to just accept the deal, rather than see their Microsoft holdings decline further. Of course, Yahoo would be under no illusions if certain shareholders just pressure it to take the lowest bid. One obvious exception: Legg Mason, which urged Yahoo to fight for a higher bid. Of course, its holdings in Microsoft are nominal (well, $99 million, so nominal by their standards).