Hi Jennifer,
I know I might catch some flak for even talking about this, but I have to keep a close watch on our competitors because they are constantly rocketing up in the SERPs from paid/spam links. For some reason it seems to take Google a while to catch them even with the new Penguin update.
I have no problems with using tricks of the trade to get advantageous results in rankings, but it irritates me to get outranked by competitors who are blatantly just buying thousands of junk links.
In each situation I use OSE to get several examples and then use:
https://www.google.com/webmasters/tools/spamreport to report them. It seems to take a week or so but each time I've reported I've seen the spammers URL tank about 50 positions.
In many situations however Google will just remove value from the junk links without penalty and you can still lose your position to the competitor if overall they have more good links than you do. Also take into consideration your onsite SEO, content quality and social signals.
Best of luck,
Jason