I'm no auto-defender of academies, but I do know one-sided reporting when I see it.
The Dispatches might have managed to unearth a few dodgy expenses, having gathered FOIs from a large number of schools, but it failed to mention all the school fraud and expenses scandals that go on, and have always gone on, in maintained schools.
For me the real question is whether these sorts of things become more common in academies, and whether they're less likely to be uncovered when the schools are regulated by central government rather than local authorities. That's still unproven, though there's no shortage of people who'll tell you its "inevitable", because they're so politically biased that they think anyone involved in running academies must be a crook.
My advice would be - if you're worried about your own school or academy, look at the accounts (including using an FOI for the expenses details if you have to) and see if you can unearth a scandal. If you do, shout about it, post it to Mumsnet, whatever you like, but if not, stop fretting.
Just for fun, here are a few non-academy examples that I found in just 10 minutes of Googling and you could do a similar exercise for any other area of public life too - (that's why we have auditors, because sometimes people get tempted to do bad stuff, get greedy, make mistakes etc) ....
www.gazettelive.co.uk/news/local-news/crooksbarn-primary-school-heads-5000-3715233
www.standard.co.uk/news/top-headteacher-held-over-500000-cuba-trip-expenses-6740813.html
www.somersetlive.co.uk/teacher-denies-school-expenses-fraud-claim/story-27580638-detail/story.html
metro.co.uk/2009/08/06/heads-sun-holiday-on-school-expenses-326355/
www.hamhigh.co.uk/news/education/camden_superhead_racks_up_1_300_travel_expenses_in_10_days_1_4235508
www.camdennewjournal.com/Jo-Shuter-appeal
www.hampshirechronicle.co.uk/news/8155388.Swindled_his_school_out_of___17_000/
www.questia.com/newspaper/1G1-208633945/school-head-s-pounds-5-000-claims-guidelines-may
www.sloughobserver.co.uk/news/13435771.Headteacher_signed_off_more_than__pound_600_expenses_to_husband/
news.bbc.co.uk/1/hi/england/west_midlands/8188049.stm
www.swindonadvertiser.co.uk/news/13424111.Swindon_primary_school_headteacher_in_court_on_fraud_charges/
www.nottinghampost.com/stapleford-school-office-manager-sandra-mayo/story-28648032-detail/story.html
www.telegraph.co.uk/news/uknews/crime/11573715/Head-teacher-tried-to-steal-30000-from-school.html
www.bbc.co.uk/news/uk-wales-south-east-wales-32531464
indexwiltshire.co.uk/former-primary-school-head-teacher-pleads-guilty-to-two-counts-of-fraud/
www.standard.co.uk/news/deputy-head-fired-over-school-fraud-hits-back-at-council-chiefs-6804583.html
www.standard.co.uk/news/former-school-head-and-his-deputy-arrested-over-16m-fraud-scandal-6572506.html
www.kentonline.co.uk/ashford/news/two-in-court-over-primary-34105/
www.belfasttelegraph.co.uk/news/northern-ireland/retired-dromara-school-principal-stanley-poots-denies-25-fraud-charges-34519187.html
www.theguardian.com/education/2011/mar/01/head-arrested-in-fraud-case
schoolsimprovement.net/former-headteacher-charged-with-five-counts-of-fraud/
www.banbridgeleader.co.uk/news/banbridge-news/ex-head-faces-string-of-fraud-charges-1-7094260