StumbleUpon is popular, delivers interested and qualified traffic and is relatively cheap for their paid inclusion program. But like other social media, StumbleUpon isnâ€™t the easiest way to promote your site. In fact, it may not even be valuable to promote your site. As StumbleUpon warns in their advertising FAQ:
Some content doesn’t work well with StumbleUpon. A hard-sell offering little introduction or supporting information will seem out of place to StumbleUpon’s community members. Remember that they’re using the service to find something new, something different. Pages that contain little more than a list of ppc or affiliate links also will not perform well.
Is it worth is to promote your site via paid inclusion on StumbleUpon? The cost is $0.05/impression. The conversion rate will obviously depend on what a conversion is for your site.