Microsoft has informed developers that Windows Phone apps and updates will now take at least one week to be approved. In its April newsletter to developers, the company states this is down to the rising volume of submissions. Although the current delays are temporary, Microsoft's Certification FAQ, updated on March 22nd, implies that once the backlog is dealt with, certification will take around a week — previously, apps would take around 72 hours from initial upload until becoming available for download.
While it makes sense that the number of apps submitted is increasing, it's possible that the company is also responding to criticism about the quality of apps in the marketplace by looking at submissions more carefully. In the past, we've found a number of fake or mislabeled applications which, while adding to the all-important app count, are exactly what it doesn't need if it wants Windows Phone to be seen as a quality platform.