Brown in particular is paying the price for his inability to come to terms with the new confessional politics. People want to know who he really is, but if what he is really is a cautious and reserved politician who plays the percentages, then the public don't want to know. So he is forced to tour the daytime-TV sofas trying to show his human side, and ends up revealing only how uncomfortable he is with the politics of self-revelation. His caution and his constant calculation make him look like a man in a mask - the classic hypocrite with something to hide.
I can't abide the "they're all cheats and liars" view of politicians (although if that's true then at least it must mean they're a reasonable sampling of the public at large). We're the people who force them into obfuscation because we're always ready to scream as soon as they propose doing anything that might not be in our personal interests. Now that everyone in public life, from politicians through football managers to union bosses and chief executives, have taken the same course in masking the unpleasant truth behind linguistic emollients we can all now sympathise with the wise words of Carrie Fisher when she said "it's hard to be sincere in Hollywood because everybody does that fake sincerity so well."