Maggot...I can understand that you may not 'get' Joe Satriani, and I assume you are not a guitar player. The fact is that he was really rather seminal as a guitar virtuoso, especially with his album 'Surfing with the Alien' which was the first shred guitar album to be publicly recognised and popular. In addition to that, he also taught Steve Vai, another successful virtuoso player, who was in bands such as Whitesnake, and The Frank Zappa Band. To add to his accolades even further, he was guitar teacher and mentor to Metallica guitarist Kirk Hammett, and you can hardly argue that they weren't successful (or good, although maybe not to everyone's tastes).
He also seems a genuinely nice guy, and I don't think he would sue them just out of spite. If someone is encroaching on your territory in a manner like this, I think it's justified to take action. He is probably hoping for an out of court settlement rather than a big proper case.
As a matter of fact, I don't find Coldplay all that bad, but they are rather repetitive, and I do think that song really does sound rather suspectly similar to 'If I Could Fly'...
