It's just insanity to even think of it.
http://www.wolframalpha.com/input/?i=2^160
In plain numbers, that first output under "Result:" is what 2^160 is. 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976.
Supposing that a quadrillion addresses have been generated (1,000,000,000,000,000), which is many magnitudes higher than the actual number generated, anyone trying to do this would have to try over 100 decillion addresses (100,000,000,000,000,000,000,000,000,000,000,000) on average before getting a single address, and the chances that that address would contain nothing because of vanity address mining are quite huge.
I understand not assuming anything about the future's capabilities, but surely a limit must be drawn at some point, by the time we could even think to have such computational power bitcoin and everything like it (the Internet as we know it, countries, governments, the human body even) would probably be obsolete.
Basically, not worth worrying about. ECDSA is the most trusted hashing algorithm, as well, because its methods mean it can't be cracked like other hashing algorithms can, so there won't be a back door. At least not before the death of the Sun/some other incredible happening that will change humanity forever.
