weheartit is wonderful site for pictures, yes. but A LOT A LOT A LOT of those pictures are NOT the person’s original work. if you look at weheartit, there’s usually a source on it that will link back to where that person found it. example:

i just went to weheartit, click on the first picture, and do you see where it says “found on” above the picture? that means the person who posted this picture found it on tumblr and is now reposting it on weheartit.
now if someone takes that picture from weheartit and posts it on tumblr, it’s essentially reposting it from tumblr, which everyone knows is really horrible because IT DOESN’T GIVE CREDIT TO THE ORIGINAL OWNER. it kind of IS giving credit to whoever posted it on weheartit, because you’re sourcing it to them if you take it from weheartit and post it on your tumblr sourcing it to weheartit.
all it is, whether you’re taking it from weheartit or posting it on weheartit, is REPOSTING from the original owner. it’s basically stealing, even if you don’t TAKE credit because you’re not GIVING credit. does that make sense?