But with B-share holders calling the shots, such firms tend to underinvest, leading to lower sales growth and valuations than with single-share-class firms, according to a study by Harvard Business School's Paul Gompers, Stanford's Joy Ishii and Wharton's Andrew Metrick.

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As to reasons for the falling out, analysts pointed to the fact that what was supposed to be a merger of equals had become effectively a takeover of Dresdner by Deutsche: the bigger bank was to have held 60-64% of the new entity, which would be called just "Deutsche Bank", with Dresdner Bank share holders owning the other 36-40%.

BBC: German bank merger off

Account-holders are not depositors but investors who get a share of an Islamic bank's revenues (and thus always get a return even if the bank were to post a loss).

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Opposition to such moves centres on the idea that public money - in the form of tuition fees backed by student loans - is going in to private hands or the pockets of share holders.

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Knowing this may influence the decision about whether the EU and IMF should require Greek bond holders to share in the pain with some form of debt restructuring, re-profiling or default.

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But Audiogalaxy is understood to have pledged to operate a "filter-in" system that only allows it to share music if it has permission from copyright holders.

BBC: Audiogalaxy moves to filter songs

The company said that the return of capital to holders will involve multiple steps, and could also include share repurchases in the open market, privately-negotiated transactions and the payment of dividends.

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