For example Elacoin's blockchain has been longer than reported by the explorer for some time and no one has said a thing about it. Without closely following a real-time explorer, you have no idea what's going on.
I think your post is mostly FUD, but I'd love to see you clarify this.
When I check
http://elc.webboise.com/chain/Elacoin - Which is just Abe scraping blocks from a live daemon, it shows block height at 21890. My other elacoin wallets show the chain at the same height, so where are you seeing the blockchain longer than reported?
Elacoin is one of the coins that had a hard fork and I'm sure there are old outdated clients in the wild. I will say that a lot of the alts don't have proper developer attention to keep attacks at bay. ELC devs had been pretty aggressive at putting updated checkpoints in source to fend off attacks. FWIW, I set up the ELC block explorer and that is my site, so I'm curious how you think it's wrong. It seems to jibe with all other ELC info I see online.