[The Saucepan Man]

Hmm. So many posts identifying Aragorn's various names, and so few considering why he acquired so many.

I don't think the issue was Aragorn hiding from the law.

No, not from "the law", but from he who would seek dominion of Middle-earth and in effect become "the law", namely Sauron.

While recuperating in Dol Guldur, and particularly after his return to Mordor, Sauron was not seeking only for the Ring. He was also seeking Isildur's heir, with whom he had a score to settle, and whom he feared. Sauron feared the return of the king - hence he was provoked into playing his hand sooner than he would have liked when Aragorn revealed to him his true identity in the Palantir.

Certainly, it made sense for Aragorn to assume an alias while in Ecthelion's service. To have revealed himself as Isildur's heir, and therefore the rightful heir to the throne of Gondor, at that stage (before the time was right for him to assume the kingship) would have destabilised Gondor and possibly led to civil war (a second kinslaying). It would probably have provoked Sauron into an immediate attack on Gondor too.

So, it was in Aragorn's interests not to let his identity slip before the time was right. It would have placed him in great personal danger, and it would probably have sealed the fate of Gondor, if not the entirety of Middle-earth, too.

While I agree with Gorwingel that the fact that Aragorn was so widely travelled led to the variety of names given to him (and this is certainly true of Gandalf too), the fact that he needed to travel incognito in the first place is, I believe, attributable to the need to conceal his true identity from Sauron and his minions.