Preved. Completely I share your opinion. It seems to me it is excellent idea. I agree with you

[Jacob]

Is there any method behind this invasion? I mean, what are they attempting to achieve?

The distribution of their links, especially to places with legitimate traffic, affect the placing of their sites in search algorithms.

Essentially, if I spam my link to whatever site all over the place, google's bots will place those sites higher in searches.