eBay: The Sweetheart of the Fund Managers

At the end of the first quarter, the last period for which figures are available, institutional investors held about 58% of eBay stock, up from about 55% at the end of the previous quarter, according to LionShares' data. During the first quarter, 10 of the top 15 institutional shareholders in eBay upped their stakes, according to LionShares.

Much of that buying likely came from index funds. Index funds hold stock in the same proportion as a particular stock index. If a company's stock price increases faster than the overall index, index funds have to buy up that stock in order to keep its value in the same proportion with the index.

Although eBay's stock shot up in the first quarter, the Nasdaq 100 index, of which it is a part, grew just 3.6%. At the end of the quarter, eBay comprised 2.53% of the Nasdaq 100 index, up from 2.06% at the end of last year.

Barclays Global Investors was among those that increased its eBay bet largely because of its representation in the Nasdaq 100. Barclay's, which holds the fifth-largest stake in eBay among institutions, bought 2 million eBay shares in the first quarter, according to LionShares. Most of Barclay's eBay shares are held in index funds, said company spokeswoman Kerry Steele. Overall, of the $746 billion in assets that Barclay's manages, about 73% are index funds, Steele said.

"We don't have an opinion on eBay because most of our active funds don't hold it," she said.

But not all institutions needed the excuse that eBay was part of an index to buy eBay shares.

Marsico Capital Management, for instance, bought all 4.5 million of its eBay shares in the first quarter, according to LionShares. A company spokesperson declined to comment on Marsico's eBay stake, but said that all of the Marsico holdings are in actively managed funds.