One of the biggest advantages of investing in small-cap stocks is the opportunity to beat institutional investors. Because mutual funds have restrictions that limit them from buying large portions of any one issuer's outstanding shares, some mutual funds would not be able to give the small cap a meaningful position in the fund. To overcome these limitations, the fund would usually have to file with the SEC, which means tipping its hand and inflating the previously attractive price.
Keep in mind that classifications such as "large cap" or "small cap" are only approximations that change over time. Also, the exact definition can vary between brokerage houses.
Investment dictionary. Academic. 2012.