Some questions out there to answer –
rmeeuwsen
– Banners should be hosted on your domain, not only is adding a call to another domain leaking pr its adding DNS lookups to every visitor you have.
– text credit to a developer is not an issue at all
– iFrames are handled by the browser, to actually open a site inside your page, so I would say this is NOT a leak as its really not even there.
Alist
– Strong links from not related sites will index very fast if the site they are on is indexed fast, makes sense but when google looks back and see’s non relevant links as a large portion of your profile it will not be good.
pjotter
– by old school are you reffering to link exchanges, directories ext? if so yes that pretty much shot but not complete out yet.