E-mails and text messages between city officials often shed light on public decisions and conduct, from how a budget is crafted to whether a mayor is taking his mistress on a taxpayer-funded vacation.

But in Dallas, it's going to be a lot more difficult to piece together clues by reviewing electronic correspondence after city officials have announced they will start scrapping e-mails that are older than 90 days off their computer servers.

"E-mails no one needs just stay on the system, and they keep growing, and growing and growing," says Deborah Watkins, city secretary, in an interview with the Dallas Morning News' David Levinthal.

But a 90-day policy makes it harder for reporters, bloggers or anyone else to investigate city hall. Often, no one understands the significance of an event until long after the fact. Say a city decides to repair a bridge that winds up collapsing three years later. Under Dallas' proposed e-mail policy, it will be harder to find out if city officials knew whether there were any problems with the construction of the bridge. They would now have a clean slate, regardless of what they might have known and communicated by e-mail.

In an interview with Levinthal, Dallas city councilwoman Angela Hunt, no stranger to e-mail requests herself, talked about the problems with the new policy.

"It can take more than 90 days for an issue to surface or become newsworthy," she said. "And if the communications about the issue are destroyed, we run the risk of not maintaining an open government."

City officials, meanwhile, complain that old e-mails simply take up too much space. D Magazine editor Tim Rogers initially joked on the Frontburner blog that city officials (third item) should use Gmail, which seemingly holds more information than the Library of Congress. Well, one reader told him that he may be on to something:

"As someone who has worked with computers his entire life, the notion of deleting e-mails (especially government e-mails) is absolutely fraudulent. You mentioned Gmail. It’s a service I am quite familiar with. After 5 years of heavy use, I’m not even above 25% of my usage.  But that is beside the point: it is well known in the IT industry that hard drive space is cheap, cheap, cheap compared to everything else (hence why Gmail just gives it away). I just checked on frys.com, and a 1TB hard drive is $100. That’s ridonkulous! Unless you’re attaching 1,000-slide PowerPoints to every e-mail, that will last forever."

Let's hope the city looks into this. Deleting old emails--especially ones that aren't even old--makes it look like you're trying to hide something. And for a city with a projected $190 million budget deficit, transparency is the one thing you don't want to cut.