Overemphasis on sub-domains causing SERP changes?

Anyone else seeing this?

[androidtech]

Recently we put up a web page on a new product. After a week it was indexed by Google and was #2. Then for a few days it was completely gone. Now it has come back in the #4 slot. What is interesting is that slots #1 - #3 are single entries all for the same domain but for different sub-domains (prefixes). I say single entries because they are not auxliary entries that are indented below a main entry. (What's the correct term for those?).

Is anybody else seeing an abundance of competitor sub-domain entries where before there was only a single entry for the domain in Google SERPs?

I wonder if this has something to do with the recent spate of changes people have seen in Google's SERPs. Perhaps an overemphasis on authority sites especially when it comes to ranking sub-domains. All of our other well ranking phrases have been unaffected, but in those areas our competitors do not have prominent sub-domains.

Not overly concerned by this, just curious.