Cablevision has a new(ish) big stakeholder and things could get interesting as it is activist investor Harbinger Capital. According to a regulatory filing Harbinger now owns a combined 11 million shares in Cablevision through two funds as of June 30th, making it the 5th largest external stakeholder in the New York cable operator.

Harbinger, lest we forget, has been shoving around the media companies in which it has snapped up stakes to find to boost share prices, notably with New York Times and Media General earlier this year.

Harbinger will be joining Mario Gabelli (pictured left), of Gabelli & Co, which owns around 20 million Cablevision shares and has been very loudly pushing for the company to consider selling assets such as its cable networks. Gabelli wants Cablevision to use the funds from such an asset sale to buy back stock. Other big name Cablevision shareholders are ClearBridge Advisors (part of Legg Mason), T Rowe Price and London-based Marathon Asset Management.

Richard Greenfield of Pali Research, who brought the Harbinger filing to our attention, makes an interesting point that the top five stake holders now own 108 million of the total 295 million float. The Dolan family, who control the company, own around 72 million.

In Greenfield’s view:

This fact will help propel Cablevision shares if they begin to buy back shares in the fall.

Too little too late, at least for 2008. Hollywood’s long awaited decision to back a winner in the single next-generation DVD wars didn’t come fast enough to stem a further decline in DVD sales this year, according to Pali Research’s Richard Greenfield.Greenfield now expects consumer spending on DVDs to fall 4 to 5 percent this year, compared to a 2 percent decline in 2007, despite an anticipated tripling of Blu-ray DVD sales this year. Blu-ray won’t start slowing the decline until 2009-2010.Slowing sales of older titles, Wal-Mart’s decision to clean up its aisles by eliminating “dump bins” of discounted titles, and anticipated Internet service bandwidth increases that could boost piracy of video are also expected to pressure sales of physical media.Perhaps there is still time for DVD and Blu-ray to make nice with consumers. Sony’s U.S. chief said consumers prefer physical discs to Internet delivery, and that it could take a decade before downloading hits its stride.(Photos: Reuters / This is what they do to pirated DVDs in Bucharest.)