Be careful when requesting stumbles, you can easily get your account and blog banned from stumbleupon, and that would be a big impact, you could lose traffic and money. Stumbleupon usually gets mad on a blog when it receives stumbles/discovers only from the same group of people. This is considered spam and you must avoid it!

I know good and strong blogs that have been banned from stumbleupon, for example dodevice.com which was is still is a powerful tech related blog, but the traffic had a significant decrease because of that ban.

How should you protect your account and blog? Well don’t ask for stumbles anymore, make some big breaks in requesting stumbles and naturally grow your profile! Stumble/discover/review everything you like! Spend some minutes per day doing that, and you’ll grow in strength.