Facebook, which is fast-headed towards a record-breaking IPO, is betting a lot on Sponsored Stories.

It’s clearly counting on the paid ads, which appear in the news feed and perhaps most importantly, be displayed to mobile Facebook users, making them the company’s first mobile ad unit ever.

For advertisers eager to experiment with Sponsored Stories, Facebook has unveiled a beta version of a Demo Tool that allows advertisers to see what their Sponsored Stories will look like on the web and Facebook’s mobile app.

Using the Demo Tool, one thing is immediately apparently: these ads are really prominent. As Simply Zesty observes, “The major feature that stands out is the amount of space that will be dedicated towards this new advertising format. Judging by the examples Facebook gives in its app and assuming that there will be other information placed beside it on the right-hand side like friends’ photos, a significant amount of space will be reserved for these adverts.”

Mobile Sponsored Stories are slightly less intrusive, as they appear further down in the news feed, but their mere presence in the news feed represents a major change to the Facebook mobile experience which has been ad-free to this point.

The big question for advertisers is whether or not Sponsored Stories will be effective. Time will tell, but if anything is certain, it’s this: Sponsored Stories are a risky proposition for advertisers. Introducing ads to one of the most personal parts of the Facebook experience (the news feed) will probably be a turn-off for many Facebook users, putting advertisers using Sponsored Stories in a precarious position. More importantly, advertisers will face the temptation to use Facebook’s Reach Generator to ensure that their ads invade even more users’ news feeds than their organic content already does.

At this point, there’s not much users can do. Facebook is going to see a lot more advertising. At a very minimum, however, users can hope that advertisers will be somewhat conscientious and use the Demo Tool to make sure their Sponsored Stories don’t look too annoying.