I'm not sure how you are drawing the conclusion that Web 2.0 Properties are automatic. I'm talking sites with quality content (not your standard 2 page setup!) that serve a purpose and give users value. These then linking to your "money site" are highly effective and will continue to be so in the future when done correctly. The issue isn't with the idea, it's not blackhat whatsoever, the issue is with most peoples implementation of the method.

With regards to link building to these properties, if you're going about it the right way you are not risking anything other than the 2.0 property itself. No footprint to your main site(s) is going to be found IF you're creating Web 2.0's in the way they should be created, organically, adding value, and not with links plastered from head to toe. If you're super cautious though- stay away from the lower quality links- still use 2.0's but opt for quality.

Even if Google suddenly decide to count Web 2.0 Properties as blackhat (They currently DO NOT providing they are done like highlighted above- Matt Cutts has confirmed this, do a quick Google search) the footprint stops with the tier 2 site, not the money site it's linking to (unless you've set the properties up idiotically - ie; ONLY linked to your site(s)...include some authority external links too..Google...Yahoo...Wiki etc)As someone who has been in the industry full time for six years, Penguin was never going to be a shock to the system. Those that evolve with the engine will survive, those that don't, won't.

XG