My reading of the news is the low-cost fund champion Vanguard is realizing ETF can cannibalizing its fund business and is fighting back.

In the past few weeks, Vanguard has listed ETFs for the growth and value components of the U.S. mid-capitalization stock market, filed for a dividend-focused offering and tweaked the tracking index for a popular emerging-markets fund.

Observers see the moves as growing evidence that Vanguard is shaking off its earlier reservations about highly targeted ETFs. As the ETF market grows, Vanguard sees eager new users of its products among such financial intermediaries as brokers and advisers.

Historically, brokers haven't flocked to Vanguard because the company's bread and butter has been selling directly to individual investors, retirement plans and institutional investors, said Dan Wiener, editor of the Independent Adviser for Vanguard Investors newsletter.

Before, brokers might lose a client to index funds. Now they can point them to ETFs such as those managed by Vanguard. Because ETFs trade like individual stocks, investors pay commissions to buy and sell shares. "Vanguard has a whole new 'customer-based' marketplace they're marketing to," Mr. Wiener said.

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The new Vanguard ETFs join a crowded field. For example, for midcap growth stocks, there are already iShares Morningstar Mid Growth Index, iShares S&P MidCap 400 Growth Index, PowerShares Dynamic Mid Cap Growth, Rydex S&P Midcap 400 Pure Growth and StreetTracks Dow Jones Wilshire Mid Cap Growth. However, the Vanguard ETFs are competitively priced with expenses of 0.13% each.