Why is it harder to stay ontop for moving companies?

[David]

I've been using a combination of blogger blogs and a local portal site that has 45,000 uniques a month to boost SEO for local Frederick MD clients.

I've found that for small local business, ones that don't have very much competition this combo is obliterating all competeting websites that dare to challenge me.

... Ok, that's the hype I use to sell my wares. For the local moving company market, well there are a half dozen 'directories' and/or moving company portals that consistently fill the at least 8 of the top ten serps for every imaginable keyword phrase.

There are only two local moving companies that show up at all with the onslaught of the movers.com yourmovers.com movingcompanies.frederickmd.com etc.

I've been able to get MY client (We Help-U-Move) to rank at least with at least ONE of the top ten, but it doens't seem to stay there.

keyword phrases are:
frederick maryland movers
frederick maryland mover
frederick maryland moving companies

movers in frederick
movers in frederick md
movers in frederick maryland
moving companies in frederick
moving companies in frederick md
moving companies in frederick maryland.

The blogs I use for everyone else serve to work as both incoming links AND additional listings in the serps.

For some reason this is not holding true for the moving industry.

Why is it working so damn well for every other niche but not this one?

I can get ranked in GoogleMaps but it doesn't stay there?

any ideas gang?
thanks