The remark about frame-breakers seems to be to bring up a valid concern - the sites being linked to certainly would not appreciate having their sites presented in a frameset with advertising which isn't their own.

If it were me (caveat: I have no credibility whatsoever) I would be concerned about the long-term viability of this as a moneymaker, given that the more popular snip.ly theoretically becomes, the more animosity it's likely to create from linked sites, and the more sites (particularly popular sites) are likely to just break out of the frameset entirely, rather than have their own SEO and analytics tampered with.