Kids poke hole in protocols that spent years peer-reviewing their way through the IETF. Implementations are about as secure as swiss cheese, but it doesn't matter since the commercial success of a security product has more to do with its channel marketing strategy than actual security. Rumors surface that some Chinese mathematicians have wrecked part of the functional toolkit we've used for the last decade in all of our products, and it's time to pack up the tents and move, again.
So a culture of nit-picking and paranoia surrounds crypto stuff. If you are using a security algorithm, so the thinking goes, it must be because there is a threat. And if there is a threat, the algorithm must be made perfectly secure.
That may be an appropriate way to think for security products. But it turns out that security techniques are often useful in general programming. MD5 is a great checksum, much better than CRCs. If you have 500 nodes in a cluster, each with some disks, yes I will guarantee you that read/write corruption can occur and get into your app. TCP packets do arrive corrupted, even though they're not supposed to.
Yes, Jenkins is faster. But it's only a 32-bit hash, whereas MD5 is 128. Yes, Whirlpool is more secure. But I don't need a 512 bit checksum. MD5 is a great compromise.
Salts and HMAC are great. But you know what? The reality is that 9 out of 10 websites store your password in the clear. It would be nice if we could get the run-of-the-mill programmer to at least understand how to hash a password before trying to scare them off with the the more advanced stuff. Otherwise they're going to throw up their hands and say their app doesn't really need to be secure anyway.
You can't say MD5 without a geek chorus shouting "It's broken, you must not use it for anything." When regular programmers don't understand the basic utility of these fat hash functions they're missing out though. The fog of confusion hanging over the security space does't benefit Joe coder who could make practical use of these tools in general applications.
The message from security folks is that you shouldn't be using any of their algs for non-secure applications. If you use their stuff, you have to go all the way.
But that's bunk. The engineering tolerances for crypto security are way beyond what the typical application needs for general purpose utility out of these functions. MD5 is a great general-purpose hash. There is useful stuff in between the extremes of a crappy CRC and and SHA-512.
So MD5 away to make your stateless GUIDs and be happy. :)