The SU community is raving about the new share tool recently introduced by StumbleUpon to motivate its users’ engagement. When it first launched I got at least 20 messages about it in my SU toolbar. My first reaction was, as expected “How cool!” but I grew to dislike the feature all together after a few days of use.

Sharing with the SU toolbar is a long, time-consuming process. But it made sense, because it “forced” relationships. The messages sent with the toolbar are personalized, whereas bulk messages sent with SU’s new share tool are neutral and cold.

Digg already has a similar tool and I can tell you that it’s nothing more annoying that to receive hundreds of “shouts” each day. The “shouters” are almost never interested in your preferences and profile: they just want diggs. I remember during the Obama campaign how many digg requests I had to ignore. With SU… I received no “request for stumbles” – politics is not a topic in my profile, my SU friends fully understood that I do not care for Obama links.

After a few days since it’s been launched, the new SU share feature no longer triggers the “how cool” reaction in me. Although I haven’t received any spam messages yet, I see that the tool is opened to exploitation, and I also see how it has the potential to destroy everything SU stands for.

StumbleUpon has probably the most interesting and most effective advertising model on the Web – a highly targeted advertising model, based on SU users’ personal interest, history of rating similar sites, location and demographics. The price, as low as 5 cents (USD) per targeted visitor made this type of advertising more than affordable. The ROI – fair (in my experience with customer sites), sometimes better than Google AdWords. This advertising model is however entirely dependent on the use of the StumbleUpon toolbar.

The problem with the new share feature is that it limits the use of the SU toolbar – it creates a sort of laziness that in the end will lead to a dangerous toolbar alienation – because it sends messages to the users via email. For example, I don’t always vote for the pages I receive when I click the “Stumble” button in the toolbar. Sometimes I just browse, looking for beautiful pages, information, anything to kill the monotony of a moment. SU is already a hub for spam pages, and MFA sites, and the new share feature will make it even more exposed.

Another curious thing: using the SU new share feature does not deliver as much traffic as using the SU toolbar. This could be just another one of those odd SU algorithm bounces, and it could be just a wrong impression I got using the feature for this short time. But assuming that this is right, for many SU users not getting the expected traffic is discouraging.

Personally, I find it very curious that SU decided to copy digg, when it is pretty clear that digg will “clone” SU’s toolbar idea with the “diggbar.”

Last but not least, www.su.pr is coming – a new shortURL service that provides short aliases for redirection of long URLs, to share StumbleUpon links on sites like Twitter and Facebook. But Digg was faster – they’ve been testing a new tinyURL-type of tool for over a month already.

With developments like this one can only wonder: are SU and Digg competing or are they actually trying to follow a common path that could, eventually, lead to a merger? What are your thoughts?