My gaming groups are typically smaller than what a typical 4E encounter usually calls for (3-4 PC's plus a DM). This in itself is not a problem, I find that I enjoy running games for smaller groups since things tend to happen at a much quicker pace. Scaling an encounter is not generally a problem either, since you can usually just drop a monster and everything will work out accordingly.
There is one thing that I do for my smaller groups, something completely non-standard, and that is award double-XP so that they may advance faster (I have yet to run a Paragon+ campaign in 4E, due to several unrelated events that will not have further mention on 1d4+5). That hasn't been a problem either; until now.
I'm running a module for my players, and at the rate they're going... well, let's just say that they're already of a high enough level for the rest of the adventure to not be a challenge. I have two basic options. One: I slash the XP awarded back to the standard 1x rating, which seems more like a punishment in some ways; or Two: build the encounters to match the PC's rate of advancement. I went with number Two.
I then had two general options for this plan. I could either simply add more monsters, or use the Monster Builder to level them up. I went with a combination of the two! For one up-coming encounter, I took the standard monster that is the threat and increased its level so that the PC's will have more of a challenge when they face it. Since I'm also designing encounters for a group of four rather than five, I have other math to figure in as well. 5 5th level monsters is a standard encounter for 5 5th level PC's, but for 4 5th level PC's its more of a challenge. Not exactly deadly, but certainly not any easier. In other words, just changing the levels to same isn't good enough, you have to make sure you keep things in scope. Especially when dealing with smaller or much larger parties. Remember, XP value alone isn't a good enough gauge when designing encounters. Despite the fact that a 5th level encounter for 10 5th level PC's is equal to 2,000 XP, that does not mean that an elite 14th level monster is a balanced encounter for those PC's.