Until the large blog publishers switch to a premium version (cost of which depends upon the number of subscribers), FeedBlitz will insert third-party ads in your email newsletters.
Lists with an active circulation of 5,000 or more must be on a FeedBlitz premium service (Pro, Turbo or Newsletter Edition).
If you're running a large list you're doing so for an organization that can afford to pay, so these changes are to encourage you to do just that. After all, the larger lists cost us more to manage, and if you're doing this professionally then it is not unreasonable for FeedBlitz to to be compensated for the work we do on your (or your organization's) behalf, especially since it's affordable to do so.
FeedBlitz vs FeedBurner Email
FeedBurner Email does seem to have an edge over FeedBlitz at the moment - the Google owned service is completely free without advertising and allows publishers to brand their email newsletters with custom logos.
Feedburner publishers also get the option to customize the look-n-feel of their newsletters. And the most interesting feature of FeedBurner Email is that it lets you decide the time when your newsletters should go out to the world.
Will DI switch from FeedBlitz to FeedBurner ? Am actually very pleased with FeedBlitz service but still thinking due to some of the reasons stated above.
Related: Always Offer the E-Mail Option