Think tanks are associated with particular parts of the political spectrum, and therefore to some extent with political parties. This means those that choose to be charities come up against the rule that charities cannot have political purposes. They mostly deal with this by making education their charitable purpose and behaving in a way that at least looks impartial - having politicians of contrasting persuasions on their boards, inviting speakers from across the spectrum and making their research freely available to all.
But from time to time things go awry and the Charity Commission conducts an investigation, often contested, as in the cases of Atlantic Bridge and the Smith Institute. The commission has often pledged to bring out special guidance but, as our analysis on pages 30 to 33 suggests, it's probably landed in the "too difficult" tray.
Is Rob Wilson warming to his work? After his seemingly diffident start, the charities minister got busier last summer and he seems set to go down as the man who finally beefed up fundraising regulation. See our interview on pages 36 to 39.
A key question for Camila Batmanghelidjh is whether she accepts she made errors. Our interview on pages 34 and 35 shows that the Kids Company founder now acknowledges what you might call good mistakes - trying to do too much and trusting what ministers said - but no bad ones, such as inept management or governance. Will she be rehabilitated? It's in the balance.
VSO is almost part of the nation's identity, like the RNLI or the WI, and is currently running the International Citizen Service, one of the government's more successful big society-style initiatives. On pages 26 to 29 we interview its chief executive, Philip Goodwin, a firm advocate of professionally-run, outcomes-driven charities. VSO's alumni, he says, are the fiercest guardians of its values and integrity.