Can a shareholder be liable in case of bankruptcy of one of the companies he invested in?
In an open corporation scenario a stock holder may well be found liable. It's a very narrow and uncommon bunch of scenarios but it's well worth sharing. See the paragraph on open corporations in the following document: http://nationalparalegal.edu/public_documents/courseware_asp_files/businessLaw/RightsOfShareholders/LiabilityOfShareholders.asp