The multi-hops incurred by Tor increases the latency, but not necessarily the throughput. Tor is slow because there are too many users leeching from a small set of altruistic relays.
Tribler is better because every user becomes a relay. It is still constrained by exit nodes (not enabled but default), which is needed to talk with non-tribler clients, but that is not a problem if the majority of peers are using tribler, and traffic is mostly in-network.
About becoming a target, I have the same worry, but I don't think that was what happened with file-sharing with search features. The problem is that search was unreliable, full of malware and spam. I think that can be solved with a Sybil resistant reputation system (the hardest part of the problem).
It is still reliant on an index, but in this case, you are building your own instead of using something public/online.
It is good for power users like you and me who have the storage to spare, but it doesn't scale, mainly for the reason that if everybody was doing it, the DHT would become a target and would be poisoned with malware, spam and fake content.