Yeah, if "Marble Blast" is not a registered trademark, then people can name other games "Marble Blast".
Even if it was, though, unless the other "Marble Blast" could be easily confused for the real thing, then I don't think it matters. And while both "Marble Blast" titles are video games, the gameplay is extremely different so they might be distinguishable enough for the trademark to not matter.
Also IAC doesn't seem to care at all about Marble Blast anyway, since they have done absolutely nothing about the fact that you can download Marble Blast Gold and Marble Blast Ultra for free on the Internet. And considering that they have supposedly owned the rights to the game for 7 years now, it's highly unlikely that they will ever do anything. After all, IAC owns so many IPs that actually generate revenue, so I wouldn't be surprised if they completely forgot that they own the rights to Marble Blast.